Heat oven to 350°F. Lightly spray 12x8-inch (2-quart) baking dish with nonstick cooking spray. Heat oil in medium skillet over medium heat until hot. Add onion and cumin; cook and stir until onion is tender. Stir in beans.
Place about 3 tablespoons bean mixture in center of each warm tortilla. Top each with 1/4 cup Monterey Jack cheese. Roll up tightly; place, seam side down, in sprayed baking dish. Spoon enchilada sauce over tortillas. Cover tightly with sprayed foil.
Bake at 350°F. for 30 to 35 minutes or until thoroughly heated. Remove from oven; uncover dish. Sprinkle with Cheddar cheese. If desired, serve enchiladas with salsa.