Heat a medium-sized oven-safe non-stick pan over medium-high heat.
Crack the eggs into a bowl, season with a pinch each of salt and pepper and whisk until combined.
When the pan is hot (but not smoking), put the butter in the pan and let it foam. Tilt the pan back and forth to cover the bottom with the melted butter.
Add the eggs, sprinkle the broccoli and feta over the eggs and put the pan in the oven. Bake until the eggs are firm and golden brown, 5-10 minutes.
Sprinkle with a pinch of pepper. Serve the frittata directly from the pan (use a trivet to protect your table) or gently slide it onto a serving plate.