Remove stems, seeds and white "ribs" from bell peppers. Cut the peppers into 1-inch wide strips. Place strips skin side up on a cookie tray. Broil until skins turn brown and bubble away from the pepper flesh. Let the peppers cool uncovered.
While the peppers cool, chop the rest of the vegetables, discarding the tomato seeds (they make the salsa gritty & watery). Mix the chopped vegetables, tomato sauce, vinegar, cilantro, and garlic powder in a big bowl.
With your fingernails or a small sharp knife, remove the skin from the roasted pepper strips. Chop the pepper strips and add them to the salsa.