For the Black Beans: Sauté the white onion and garlic. Add the black beans, spices, brown sugar, tomato purée, beef stock, and diced tomato. Simmer until thickened. Stir in fresh coriander and lime juice.
For the Pineapple Pico De Gallo: Combine finely chopped red onion, fresh pineapple, jalapeños, fresh coriander, and tomato. Dress with olive oil, lime juice, and salt.
For the Simple Guac: Mash avocado with lime juice and salt.
Assemble the quesadillas by filling tortillas with the black bean mixture and grilling until golden and crispy.
