Lightly whisk the eggs in a small bowl with a pinch salt and ground pepper.
Roughly chop the Chorizo.
Put the Chorizo pieces in a frying pan and gently heat over medium-low heat. Stir occasionally until the sausage has released its fat. Add the tomatoes and cook for a couple of minutes until tender.
Pour in the egg mixture, letting it spread out evenly.
Put a lid on and cook for about 8 minutes over low heat, until the surface of the omelette is solid. Add thee grated cheese, if used, then the rocket and fold in half.
Cook for another minute then slide it to a plate.
Cut the omelette in half and serve.