Mash or slice the avocado
Drain and rinse the black beans
Chop the onion, tomato, and cilantro if using
Lay one tortilla on a clean surface
Spread a layer of shredded cheese over half the tortilla
Add black beans, avocado, onion, and tomato evenly on top
Season lightly with salt and pepper
Fold the tortilla in half over the filling
Heat a nonstick skillet over medium heat and add a small amount of olive oil
Place the folded quesadilla in the skillet
Cook 2–3 minutes per side, or until golden brown and the cheese is melted
Remove from skillet and let it cool slightly before cutting
Cut each quesadilla into wedges
Garnish with fresh cilantro and serve with sour cream/Greek yogurt and lime wedges
