1.Parboil the potatoes for 10-12 minutes. Allow them to cool slightly. In a cast-iron or ovenproof frying pan sauté the onions in the olive oil until soft and translucent, adding the garlic towards the end.
2.Now add the bacon (or chorizo) and continue to cook until brown but not crisp. Slice the potatoes and add them to the mix, allowing them to cook some more and become a little brown from the onion bacon mix.
3.When they seem cooked through add the capsicum and pour over the combined eggs and milk. Season with salt, pepper, cayenne and chilli. On the lowest possible heat let the omelette cook until it appears partially set.
4.Arrange tomatoes on the surface of the omelette. Put the pan under a hot grill the omelette will puff up and turn a lovely golden brown. Test with a knife to ensure there are no runny eggs still inside and allow to set for 5 minutes before serving.