Heat the olive oil in a saucepan, add the onions, garlic and peppers and cook for about 2 minutes. Then let it cool down a little and then use the mixer or hand blender to make a cream. Put back in the pot and heat a little more.
Add the tomatoes and the slightly chopped sardines, season with salt, pepper and basil, stir carefully and simmer or simmer for about 5 minutes over low heat. Possibly add some water so that it doesn`t burn.