Tomatoes, Peppers and Onions (Peperonata)

Toss marinated olives into this dish if you like.

2 medium onions, sliced
2 tablespoons olive oil or vegetable oil
3 medium green bell peppers, cut into strips
1 teaspoon dried basil leaves
1 teaspoon red wine vinegar
1/2 teaspoon salt
1/4 teaspoon pepper
2 medium tomatoes, coarsely chopped

Cook and stir onions in oil in skillet until tender; add remaining ingredients except tomatoes. Cover and cook over low heat 10 minutes. Add tomatoes. Cover and simmer until green pepper is tender, about 5 minutes. Garnish with ripe olives if desired.