Crack the eggs into a small mixing bowl and whisk them until the whites and yolks are just combined, feeling smooth and slightly frothy.
Sprinkle a pinch of salt and some black pepper into the eggs, and give them a quick stir to incorporate the seasonings.
Heat the non-stick skillet over medium heat and add a teaspoon of olive oil, swirling to coat the bottom.
Add the chopped spinach to the skillet and sauté for 1-2 minutes, stirring gently, until the leaves wilt and turn vibrant green.
Pour the whisked eggs evenly over the sautéed spinach, tilting the pan slightly to spread the eggs into a thin, even layer. Let it cook gently for about 1-2 minutes until the edges start to set and turn lightly golden.
Sprinkle crumbled feta cheese across one half of the omelette, distributing it evenly so every bite gets a salty, creamy touch. Add the wilted spinach on top of the feta.
Let the eggs cook for another 1-2 minutes until the top is just set but still slightly jiggly, then gently fold the omelette in half over the fillings using the spatula.
Cook for another 30 seconds to 1 minute, allowing the cheese to melt slightly and the omelette to finish cooking through. Carefully slide it onto a plate.
Let the omelette rest for about a minute to settle, then sprinkle with extra black pepper or herbs if desired, and serve immediately while warm.
