Heat oil or butter in a skillet over medium heat
Add chopped onion and cook until softened
Add chopped garlic and cook briefly
Add diced peppers or tomatoes if using
Stir in torn or chopped corn tortillas
Cook until the tortillas are lightly crisp
Beat eggs in a bowl with salt and pepper
Pour the eggs into the skillet
Stir gently until the eggs are just set
Add shredded cheese if desired
Mix in cilantro, salsa, or cooked chorizo if using
Serve hot with avocado, beans, or extra salsa