Drain black beans into a colander. Set aside briefly.
In a skillet, heat 2 tablespoons of olive oil until shimmering. Add garlic powder, cumin, and chili powder. Sauté until fragrant (about 1 minute), stirring continuously to prevent spices from burning.
Add black beans to the skillet. Toss beans to coat with the oil, then saute a few minutes until warmed through, stirring as needed.
Mash the beans with a potato masher until no longer whole and starting to become creamy. Add 3-4 tablespoons of water, continuing to mash until you get a bean puree (there can still be a few chunks of beans).
Add salt and pepper to taste (optional).
Meanwhile, heat another skillet over medium heat (or wash and use the same skillet) and add ½ teaspoon of oil or butter and place a tortilla in the pan. Spread about 1/4 of the black bean mixture onto half of the tortilla. Sprinkle evenly with 1/2 cup cheese and fold the other half over. Cook for about 2 minutes, pressing down with the back of your spatula to help seal the quesadilla as the cheese melts. Flip, and cook another 2-3 minutes, or until cheese is melted and tortilla is golden and crispy. Reduce the heat if the tortilla is browning too quickly.
Remove from heat and slice into triangles or strips with a pizza cutter. Continue with remaining tortillas. Enjoy with sour cream or Greek yogurt, salsa, guacamole or as is.