Start by finely chopping your onion, red bell pepper, and green bell pepper. Dice the tomato, removing the seeds, and rinse the black beans.

In a non-stick skillet over medium heat, add cooking oil or butter. Sauté the onion for about 3 minutes, then add the bell peppers and cook for an additional 2 minutes. Stir in the tomato, black beans, sausage (if using), and spices for 3-4 minutes until warmed through.

In a mixing bowl, crack 4 eggs and add milk, salt, and black pepper. Whisk for 1-2 minutes until fluffy.

Wipe the skillet clean and return to medium heat, adding more oil or butter if needed. Pour in the egg mixture and swirl to spread it evenly. Cook for 1-2 minutes until set around the edges.

Spoon the filling onto one half of the omelette and add cheese. Fold the omelette over and cook for another minute until the cheese melts.

Transfer the omelette to a plate and garnish with cilantro, avocado, and salsa. Serve with lime wedges.