Preheat the oven to 450°F. Arrange a rack in the center of the oven. Measure a piece of parchment paper big enough to line the bottom of a big, heavy baking sheet and set it aside. Place the unlined baking sheet in the oven to heat up as the oven preheats.

Spread refried beans on one side of each tortilla, about 1 heaping tablespoon per tortilla, and arrange in a single layer on a platter or another baking sheet. Dust each one with chili powder, if using. Put the cheese in a convenient location.

Remove the preheated baking sheet from the oven, line it with parchment, and spray generously with cooking spray. Arrange the tortillas on the baking sheet in a single layer, bean side up, and top each tortilla with cheese, about ¼ cup per taco mounded in the center.

Place the baking sheet in the oven and bake until the cheese has melted and the tortilla is soft, about 1 to 2 minutes. Remove from the oven and fold each tortilla over to make tacos.

Return the tacos to the oven and bake until lightly crisp on the bottom, 5 to 7 minutes. Flip and cook until gooey with crispy cheese bits, another 5 to 7 minutes.

Let cool for a few minutes. Serve with salsa, sour cream, and/or guacamole for dipping or topping.