Start by washing and chopping all the vegetables. Dice the bell pepper, onion, and spinach into small, even pieces. This helps everything cook evenly and blend well into the eggs.
Heat olive oil in a skillet over medium heat. Add the onion and bell pepper, cooking until soft and fragrant. Stir occasionally to prevent browning and allow natural sweetness to develop.
Stir in the chopped spinach and black beans. The spinach will wilt quickly, and the beans will warm through. Keep stirring gently to distribute everything evenly.
In a bowl, whisk the eggs with milk, salt, and pepper. Pour the mixture into the skillet with the vegetables. Lower the heat slightly and stir slowly to create soft, fluffy curds.
Sprinkle the grated cheese over the eggs and gently fold it in. Cook just until the cheese melts and the eggs are set but still tender.
Heat the tortillas in a dry pan or tortilla warmer. Warm tortillas are more flexible and enhance the overall eating experience.
Spoon the egg and veggie mixture into each tortilla. Add your favorite toppings and serve immediately while warm.