In a large bowl, mash pinto beans. Stir in 3/4 cup salsa and garlic.
In a separate bowl, mix together 1/4 cup salsa, cilantro, black beans and tomatoes.
Place 1 tortilla in a pie plate or tart dish. Spread 3/4 cup pinto bean mixture over tortilla to within 1/2 inch of edge. Top with 1/4 cup cheese, and cover with another tortilla. Spread with 2/3 cup black bean mixture, and top with 1/4 cup cheese. Repeat layering twice. Cover with remaining tortilla, and spread with remaining pinto bean mixture and cheese.
Cover with foil, and bake in preheated oven for about 40 minutes. Cut into wedges, and serve with salsa and sour cream.