In a medium nonreactive bowl, mix onions, tomatoes, taco mix and black beans. Toss pasta with olive oil. Spread 1 cup tomato mixture on bottom of baking dish. Add cooked pasta. Dot with ricotta and then spread with a knife. Stir chicken pieces into remaining tomato mixture and spoon over ricotta. Sprinkle with shredded cheese. Bake 25 to 30 minutes. Serve immediately. From Sun-Sentinel Food Section, Thursday, July 20, 1995 "Meals in Minutes"