Crack the eggs into a bowl, add salt and pepper, then whisk until well blended.

Heat olive oil in a non-stick skillet over medium heat.

Add onions and bell peppers to the skillet; sauté for 2-3 minutes until softened.

Add diced tomatoes and spinach; cook for another 1-2 minutes until spinach wilts.

Pour the beaten eggs evenly over the vegetables in the skillet.

Cook for 2-3 minutes until the eggs begin to set around the edges.

Sprinkle shredded cheddar cheese over the eggs.

Carefully fold the omelet in half and cook for another 1-2 minutes until cheese melts and eggs are fully set.

Slide the omelet onto a plate and serve immediately.