Chop all the vegetables and set aside.

In a mixing bowl, whisk together the eggs, salt, and black pepper until well combined.

Heat olive oil in a non-stick skillet over medium heat. Add the onions and bell peppers, sautéing until soft.

Add the spinach and tomatoes, cooking until the spinach wilts.

Pour the whisked eggs over the cooked vegetables in the skillet. Cook until the edges start to set.

Sprinkle shredded cheese over the omelette. Once the cheese melts and the eggs are fully set, fold the omelette in half and serve.