My first encounter with an onion tart wasn’t quite love at first bite. It was a single-layered, slightly sad affair that left me wondering what all the fuss was about. But then, a few years later, I stumbled upon a recipe that promised “double the flavor” and “two layers.” Skeptical yet intrigued, I gave it a shot. And oh, what a difference! That experience completely transformed my view of onion tarts, turning a once-unimpressive dish into a cherished favorite. This recipe, dear reader, is my ode to that revelation. It’s an Onion Tart that genuinely delivers on its promise of double the deliciousness, showcasing how a simple design tweak can elevate a classic to new heights.
Why you’ll love this dish
This isn’t just another onion tart; it’s a testament to how intelligent layering can create an extraordinary culinary experience. You’ll adore this recipe for its rich, caramelized onion flavor that runs deep, complemented by the creamy, savory custard that binds it all together. The “why two is better than one” isn’t a gimmick; it’s the secret to an incredibly satisfying texture and an intensified onion presence in every bite. It’s sophisticated enough for a dinner party appetizer, yet comforting enough for a cozy weeknight meal alongside a simple salad.
> “I thought all onion tarts were created equal until I tried this recipe. The double layering truly makes a difference – it’s so much more flavorful and satisfying. A new family favorite!”
The cooking process explained
Creating this Onion Tart involves a few key steps, each contributing to its ultimate deliciousness. First, you’ll begin by getting friendly with your onions, slowly caramelizing them to draw out their natural sweetness and depth of flavor. This isn’t a step to rush; patience here reaps immense rewards. Next, we prepare a simple yet flavorful custard that will become the luxurious binder for our onions. The real magic happens when we tackle the “double” aspect: spreading a layer of onions, then a portion of the custard, followed by more onions, and finally, the remaining custard. This ensures that every forkful is perfectly balanced with onion and creamy goodness, baked all together in a flaky pastry shell until golden brown and irresistibly fragrant.
What you’ll need
Key Ingredients:
- For the Pastry:
- 1 ½ cups all-purpose flour
- ½ teaspoon salt
- ½ cup (1 stick) unsalted butter, very cold and cut into small pieces
- ¼ cup ice water (or a little more, as needed)
- For the Filling:
- 4 large yellow onions (about 3 lbs), thinly sliced
- 2 tablespoons olive oil
- 1 tablespoon unsalted butter
- ½ teaspoon salt, plus more to taste
- ¼ teaspoon black pepper, plus more to taste
- 2 large eggs
- 1 cup heavy cream
- ½ cup whole milk
- ¼ cup grated Gruyere cheese (optional, but highly recommended)
- Pinch of nutmeg
Directions to follow
- Prepare the Pastry: In a large bowl, whisk together the flour and salt. Cut in the cold butter using a pastry blender or your fingertips until the mixture resembles coarse crumbs with some pea-sized pieces of butter remaining. Gradually add the ice water, 1 tablespoon at a time, mixing until just combined and the dough comes together. Do not overmix. Form into a disc, wrap in plastic, and refrigerate for at least 30 minutes.
- Caramelize the Onions: In a large, heavy-bottomed skillet or Dutch oven, heat the olive oil and butter over medium-low heat. Add the sliced onions, ½ teaspoon salt, and ¼ teaspoon pepper. Cook slowly, stirring frequently, for 30-45 minutes, or until the onions are deeply golden brown and very soft. If they start to brown too quickly, reduce the heat. Remove from heat and set aside to cool slightly.
- Pre-bake the Crust (Blind Bake): Preheat your oven to 375°F (190°C). On a lightly floured surface, roll out the chilled dough into a 12-inch circle. Carefully transfer it to a 9-inch tart pan with a removable bottom. Trim the edges. Line the crust with parchment paper and fill with pie weights or dried beans. Bake for 15 minutes. Remove the weights and parchment, and bake for another 5-7 minutes, until the crust is lightly golden.
- Prepare the Custard: While the crust is pre-baking, in a medium bowl, whisk together the eggs, heavy cream, milk, Gruyere (if using), and nutmeg. Season with a pinch of salt and pepper.
- Assemble the Tart: Spread half of the caramelized onions evenly over the bottom of the pre-baked tart crust. Pour about half of the egg custard mixture over the onions. Top with the remaining caramelized onions, spreading them out. Gently pour the remaining custard over the top, wiggling the pan slightly to ensure the custard fills all the gaps.
- Bake the Tart: Reduce the oven temperature to 350°F (175°C). Bake for 35-45 minutes, or until the center is just set (a knife inserted near the center should come out clean) and the top is golden brown.
- Cool and Serve: Let the tart cool on a wire rack for at least 15-20 minutes before slicing and serving. This allows the custard to fully set.
Best ways to enjoy it
This double-layered Onion Tart is wonderfully versatile. It shines as an elegant appetizer, cut into small squares or wedges, perhaps garnished with a sprinkle of fresh chives. For a more substantial meal, serve a larger slice alongside a crisp, peppery arugula salad simply dressed with a lemon vinaigrette, which provides a lovely counterpoint to the tart’s richness. It’s also fantastic for a weekend brunch spread, offering a savory alternative to sweeter pastries. Pair it with a light white wine like a Sancerre or a crisp rosé if serving at dinner.
How to store & freeze
To keep your Onion Tart tasting its best, allow it to cool completely before storing. Wrap any leftover slices tightly in plastic wrap or aluminum foil, or place them in an airtight container. It will keep well in the refrigerator for up to 3-4 days.
Reheating: To reheat, place individual slices in an oven preheated to 300°F (150°C) for about 10-15 minutes, or until warmed through. You can also microwave it, but the crust won’t be as crisp.
Freezing: This tart freezes surprisingly well. Once completely cooled, you can wrap individual slices or the entire tart (if preferred) tightly in several layers of plastic wrap, then a layer of aluminum foil. Freeze for up to 2-3 months. Thaw overnight in the refrigerator before reheating as directed above.
Practical cooking tips
- Patience with Onions: The absolute key to a truly incredible onion tart is perfectly caramelized onions. Don’t rush this step. Low and slow heat is your friend here, unlocking deep, sweet flavors.
- Don’t Overfill: Be mindful not to overfill your tart pan with the custard. Leave a small amount of space at the top, as the custard will expand slightly during baking.
- Cool Before Slicing: It’s tempting to dive right in, but letting the tart cool for at least 15-20 minutes after baking is crucial. This allows the custard to set properly, preventing it from oozing out when you cut into it.
- Prevent a Soggy Bottom: Blind baking the crust as directed is essential. For extra insurance, you can brush the pre-baked crust with a thin layer of egg white before pouring in the filling; this creates a barrier against moisture.
Creative twists
- Cheese Please: While Gruyere is fantastic, experiment with other cheeses! Sharp cheddar, aged provolone, or even a crumbling of goat cheese could add delightful new dimensions.
- Herbaceous Notes: Stir in some fresh thyme or rosemary with the onions during the last few minutes of caramelization for an aromatic upgrade. A sprinkle of fresh chives or parsley after baking also adds freshness.
- Meat Lover’s Twist: For a heartier version, cook a few strips of chopped bacon or pancetta until crispy, then crumble them into the onion filling before baking.
- Spice It Up: A tiny pinch of red pepper flakes with the onions or a dash of smoked paprika in the custard can add a subtle warmth and complexity.
Common questions
How do I know when the tart is fully cooked?
The best way to tell if your onion tart is done is to gently jiggle the pan. The edges should be set and firm, and the center should have only a slight, very subtle jiggle. You can also insert a thin knife or skewer into the center; if it comes out mostly clean, it’s ready.
Can I use a store-bought pie crust?
Absolutely! While a homemade crust is lovely, a good quality store-bought pie crust or puff pastry sheet can save you time and still yield a delicious result. If using puff pastry, gently prick the bottom with a fork before blind baking.
My onions are browning too quickly, what should I do?
If your onions are browning too fast before they soften, your heat is too high. Reduce the flame and add a tablespoon or two of water or chicken broth to the pan. This will help deglaze the pan and create steam, allowing the onions to continue cooking down without burning. Continue stirring regularly.
Classic Gruyère and Thyme Onion Tart
Equipment
- large bowl
- pastry blender
- plastic wrap
- rolling pin
- 9-inch tart pan
- parchment paper
- pie weights or dried beans
- large skillet or Dutch oven
- whisk
- wire rack
Ingredients
For the Pastry:
- 1 ¼ cups all-purpose flour
- ½ teaspoon salt
- 8 tablespoons unsalted butter, very cold and cubed
- 3-4 tablespoons ice water
For the Filling:
- 3 large yellow onions about 2 lb
- 2 tablespoons unsalted butter
- 1 tablespoon olive oil
- ½ teaspoon salt plus more to taste
- ¼ teaspoon freshly ground black pepper plus more to taste
- nutmeg Pinch
- 3 large eggs
- 1 cup heavy cream
- 1 cup grated Gruyère cheese divided
- 1 tablespoon fresh thyme leaves, chopped optional, for garnish
Instructions
Prepare the Pastry
- Whisk together flour and salt, then cut in cold butter until crumbly.
- Gradually add ice water until the dough forms, then refrigerate for at least 30 minutes.
Roll out the Pastry
- Roll dough to an 11-12 inch round and transfer to a 9-inch tart pan with a removable bottom.
- Press into the pan, trim excess, prick the bottom with a fork, and chill for 20 minutes.
Blind Bake the Crust
- Preheat oven to 375°F (190°C), then line the pastry shell with parchment and pie weights.
- Bake for 15 minutes, remove weights and parchment, then bake for another 5-7 minutes until golden.
- Cool slightly and reduce oven temperature to 350°F (175°C).
Caramelize the Onions
- Melt butter and olive oil in a large skillet over medium-low heat, then add sliced onions and salt.
- Cover and cook for 10-15 minutes until softened, then uncover and cook for 25-35 minutes until deep golden brown.
- Let cool slightly.
Make the Custard
- Whisk together eggs, heavy cream, salt, pepper, and nutmeg in a medium bowl.
- Stir in ¾ cup of Gruyère cheese, reserving the rest for topping.
Assemble the Tart
- Spread cooled caramelized onions evenly over the blind-baked pastry shell.
- Pour the custard mixture over the onions, then sprinkle with the remaining Gruyère cheese.
Bake the Tart
- Bake at 350°F (175°C) for 35-45 minutes, or until the custard is set and golden brown.
- If browning too quickly, loosely tent with aluminum foil.
Cool and Serve
- Remove from oven and cool on a wire rack for 15-20 minutes before slicing.
- Garnish with fresh thyme leaves if desired.