1. Drain black beans and sprinkle with chili powder, cumin and a little salt and pepper. Swirl oil in skillet and add garlic and chopped onion and saute until soft. Add black beans and stir until heated through.
2. Sprinkle half of 1 tortilla with 1/4 cup cheese, 1/4 of the bean mixture, and top with 1/4 cup more cheese. Fold in half and repeat with remaining tortillas.
3. Heat 1 tbsp oil in two large skillets over med-high heat. Place 2 folded tortillas in each skillet and cook until brown and cheese melts, about 4 minutes per side.
4. Transfer quesadillas to a plate and cut into wedges. Serve with salsa. Optional sides: sour cream and cilantro.