Carefully separate the egg whites from the yolks. You can do this by cracking the eggs and transferring the egg whites into a clean bowl while discarding the yolks.
Whisk the egg whites in a bowl until they become slightly frothy. This will make your omelette light and fluffy.
In a separate bowl, combine the diced bell peppers, onions, tomatoes, and chopped spinach. These colorful vegetables will add flavor and nutrients to your omelette.
Heat a non-stick skillet over medium-low heat. You can use cooking spray or a small amount of olive oil to prevent sticking.
Once the pan is heated, pour in the whisked egg whites. Allow them to cook undisturbed for a minute or two until the edges start to set.
Sprinkle the vegetable mixture evenly over one-half of the omelette.
Season the egg whites with salt and pepper. Carefully fold the other half of the omelette over the vegetables, creating a half-moon shape.
Continue cooking for another 2-3 minutes or until the omelette is fully set, but still slightly fluffy in the center.
If you're using cheese, sprinkle it over the omelette just before folding it in half. The residual heat will melt the cheese.
Carefully slide the omelette onto a plate, and it's ready to serve. Garnish with extra fresh herbs or a dash of hot sauce if desired.