Wash the tomatoes (and spring onions or chili if you’re using them) and chop into small pieces.
Heat oil in a pan and fry the tomatoes for about 2 minutes. Set aside. Clean the pan with a tissue.
Crack the eggs into a bowl and beat well with a fork, adding the salt and pepper
Heat the rest of the oil in a pan (non-stick if possible) on low to medium heat
Pour the egg mix into the pan
Using a spatula, ruffle the omelette so it doesn't stick. As you create gaps tilt the pan so the liquid fills the spaces.
Let it cook for about 2 minutes and...
Here's the important part: when the egg mixture looks nearly cooked (but there's still just a tiny bit of runny egg left) drop on the tomatoes and basil (and cheese, spring onions or chili if you’re using them).
Fold the empty half of the omelette on top of the other.
Slide it onto a plate - the heat from closing the omelette will finish cooking the inside.