Crack the eggs into a bowl and beat them well with salt and pepper.
Finely chop onions, bell peppers, and other vegetables.
Add butter to a pan and sauté the vegetables.
Once the vegetables are cooked, pour the beaten eggs into the pan.
Cook over medium-low heat, gently shaking the pan.
When the eggs are half-cooked, add cheese and fold the omelette in half.
Cook until the outside is lightly golden.
Transfer to a plate.