Heat a little butter and oil in a frying pan, add the onions and soften them. Stir in the chillies or chilli powder, fry for a minute or two and then add the tomatoes, garlic, seasoning and herbs.
Simmer uncovered until you have a thickish sauce, remove the herbs and sieve or liquidise.
Reheat in the same pan before serving. This can be ferociously or gently hot according to how