Set pan to medium heat. Add butter.
Sauté spinach and tomato until spinach is wilted.
Add two eggs, mozzarella, salt, and pepper.
When the egg is about 90% cooked, add the tortilla and gently press it down.
Turn over the tortilla once the egg is ready.
Reduce heat to medium and brown the tortilla slightly.
Put it on a plate, roll it up, and serve it.