When her local market had short ribs on sale, Mickey Strang decided to turn them into an easy Sunday dinner. You'll need to have the ribs sawed into chunks at the market.
Rinse ribs and pat dry; trim off and discard excess fat. In a 9- by 13-inch casserole, mix garlic, tomato paste, tequila, and tomato juice; turn ribs over in sauce to coat well. Cover airtight and chill at least 1 hour; if marinating up to 1 day, turn ribs over several times.
Uncover ribs, turn over in sauce, and sprinkle with onions and chilies. Seal casserole tightly with foil.
Bake in a 350° oven until meat is very tender when pierced, 2 1/4 to 2 1/2 hours. Skim off and discard fat; season meat to taste with salt and pepper.