In a large bowl, whisk the eggs until the whites and yolks are completely combined. Place a large skillet over medium heat and add enough butter or olive oil to coat the bottom. When the butter is melted or the oil is hot, pour in the eggs and stir occasionally until the eggs are cooked. Stir in a pinch of salt and a generous amount of black pepper, then transfer to a large plate to cool to room temperature.

Rinse or wipe down the skillet, place it back over medium heat, and add another pat of butter or oil. Add the spinach and cook, stirring often, until the spinach is just wilted. Spread the cooked spinach on another large plate to cool to room temperature.

Arrange a tortilla on a work surface. Add the eggs, spinach, tomatoes, and feta down the middle of the tortilla and tightly wrap.