Line a baking sheet with foil; set aside. Preheat the oven broiler to high with the rack set 4 inches from the heat source.
In a blender or food processor, combine the black beans, salsa, ricotta cheese, red onion, cilantro, and lime juice, and blend until smooth but thick.
Spread the black bean mixture among the bagel halves. Sprinkle with cheddar cheese. Place under the broiler and broil for 1 minute or until the cheese melts.
Remove the bagels from the broiler. Top each bagel with sliced avocado and about 2 tsp. of yogurt. If desired, sprinkle with chili powder.