Taco Chip Dip

1 pound ground beef or ground turkey                           
1 onion, chopped                                                                   
16 ounce can tomatoes, drained and chopped                           
1-1/4 ounce package taco seasoning                                                               
4 ounces (1 cup) shredded Cheddar cheese
8 ounces pasterurized process cheese spread, cut up                       
8 ounces (2 cups) shredded Mozzarella cheese

Heat oven to 350. In medium skillet, brown ground beef and onion; drain well. Stir in tomatoes and taco seasoning; simmer 15 minutes. Combine cheeses; layer meat mixture and cheeses in shallow baking dish. Bake 3 to 5 minutes or until cheeses are melted. Serve hot with plain taco chips.