Heat olive oil or butter in a small non-stick skillet over medium-low heat.
Whisk eggs with a pinch of salt and pepper in a bowl until just combined.
Pour eggs into the skillet and let them set for about 30 seconds without stirring.
Add the chopped spinach and crumbled feta cheese over the eggs.
Gently push cooked edges towards the center with a spatula, allowing uncooked egg to flow underneath, and cook for 2-3 minutes until mostly set but still moist.
Remove the skillet from heat immediately to prevent overcooking.
Serve hot, optionally with a slice of whole-wheat toast.
Notes
For extra flavor, try adding a dash of hot sauce or a sprinkle of fresh herbs like chives or parsley.