01 - Melt the butter in a nonstick skillet over medium heat. Add the spinach and cook until wilted, about 1 minute.
02 - Whisk the eggs in a mixing bowl with a pinch of salt and black pepper until fully combined.
03 - Pour the beaten eggs into the skillet, tilting to evenly coat the surface. Allow the eggs to set around the edges while remaining slightly soft in the center.
04 - Spoon the wilted spinach and crumbled feta evenly over half of the omelette. Fold the omelette in half, then cook for an additional 30 seconds until the cheese begins to soften.
05 - Slide the omelette onto a plate and serve immediately while hot.