Heat olive oil in a saucepan. Sauté onions (cut into half rings) at low temperature.
In the meantime, clean and dice the peppers, add them to the onions and sauté for another 10 minutes.
Then add peeled tomatoes and dry white wine, stew again for 5 minutes until soft. Later increase the temperature and cook, stirring, until most of the liquid has boiled away.
Later season with salt, pepper and chili powder.