Mix spices together in a small bowl and set aside.
Heat half the olive oil in a skillet over medium heat. Add onions and cook until softened.
Add garlic, bell pepper, and spices and stir for 1 minute.
Add beans and vegetable broth. Mash about ⅔ of the beans so the mixture thickens and holds together. If the mixture is too wet, continue cooking while stirring until the mixture thickens and dries out a little.
Remove from heat. Taste and add salt as desired.
Preheat oven to 400°F. Lightly grease a baking sheet with half the remaining olive oil.
Spread some of the filling on one side of a tortilla. Sprinkle cheese on top if desired. Fold the tortilla over and press down to help it stick. Place on baking sheet and repeat with remaining filling and tortillas.
Brush the remaining olive oil on top of the quesadillas.
Bake for 10 minutes or until the bottom browns, then flip and bake another 5-10 minutes until crispy.
Stovetop option: If you don't want to use the oven, you can cook the quesadillas in a pan on the stove. They should take about 3-5 minutes per side. Stovetop will be faster but less crispy.
Notes
1) Beans: Use any bean you like. Kidney beans, black beans, pinto beans, or even lentils will work.2) Vegetable Broth: I use water + 1/4 tsp vegetable bouillon.