01 -
Peel the onion, then slice it thin. Chop the garlic finely. Cut the bell peppers in half, clean out the seeds and white bits, and slice into thin strips about ¼ inch (6 mm) wide.
02 -
Warm up the olive oil in a pan over medium-low heat. Toss in the onion and gently cook it for about 5 minutes, stirring every now and then so it doesn’t stick. Add the garlic and keep cooking for another 5 minutes, making sure it gets soft but doesn’t brown.
03 -
Put the bell pepper strips into the pan. Mix them well and let them cook gently for about 10 minutes. Pour in the tomato puree, throw in half the salt and the black pepper, then stir again. Cover it up with a lid and simmer on low heat for 30-40 minutes, stirring now and then.
04 -
Take off the lid and stir in the sugar and white wine vinegar. Let everything simmer uncovered for another 10 minutes so the sauce thickens up a bit and the peppers become nice and soft. Taste it, add more salt if needed, and serve warm or let it cool to room temp before enjoying.