Beat the eggs in a bowl with salt and pepper to taste. 

In a small skillet over medium heat, melt the butter and then add in the onions to saute them until slightly golden. 

Add in the eggs while you move the pan in a circular motion so that the eggs are distributed well and do not stick to the bottom of the pan.

Shred the mozzarella with your hands, (or if you wish cut it into small pieces before hand), and add it on top of the eggs in the pan.

Next put the 2 tablespoons of fried tomato in the center of the omelette.

Depending on how you like your eggs, either flip it over or remove it from the heat when the eggs arecooked to your satisfaction. In my case, I removed it after the eggs had cooked well and turned a golden color on the bottom. 

Lastly, place your omelette on a plate and add a little more pepper to taste (optional).