A quesadilla does not need a thick layer of plant cheese if the filling already holds together. Coarsely mashed beans do much of that work, leaving the tortilla crisp and the middle soft.
Drain a 400 g tin of black beans. Mash with two tablespoons salsa, half a teaspoon cumin, and a little salt if needed. Spread across one half of each of four small vegan tortillas, leaving a narrow border. Add a small amount of chopped spring onion and fold over.
Cook in a lightly oiled frying pan over medium heat, pressing gently with a spatula. Turn carefully once the underside is golden and continue until the filling is hot. A very high heat can burn the tortilla while leaving the beans cold.
Cut into wedges and serve with chopped tomato or extra salsa. Keep watery additions outside the tortilla; they tend to make the seam leak and the inside soggy. Check packaged tortillas for ingredients rather than assuming every brand is vegan.