Peel and finely chop the onion, cook in a saucepan in a tablespoonful of olive oil until soft but not browned. Peel the garlic cloves and crush them in a garlic crusher, stir into the cooking onion after five minutes or so.
Cut the peppers into two lengthways, cut out and discard the pith, cut into thin strips, and add to the onion mixture when the onion is soft. Continue to cook over a low heat, stirring from time to time.
Meanwhile put the tomatoes into a jug of boiling water, and wait for 20 seconds or so. Remove the tomatoes one by one, remove and discard the skin, cut into quarters, remove and discard the pips but retain as much of the juice as possible.
Add the tomato pieces and juice to the onion mixture and simmer covered until the tomatoes are soft, mashing them down every now and again with a wooden spoon. When ready stir in the smoked paprika and chopped oregano and season with salt and pepper. This is now ready to use but will tolerate being rewarmed if necessary.