Drain the black beans and add them to a bowl along with the frozen corn (no need to thaw)
Finely dice the onion, mince the garlic, and roughly chop the cilantro.
Add the onion, garlic, cilantro, shredded cheddar, and taco seasoning to the bowl with the beans and corn. Stir until everything is evenly combined and coated in seasoning.
Place a half cup of the filling on one side of each tortilla and fold over. Cook the quesadillas in a skillet over medium heat on each side until brown and crispy and the cheesy filling has melted. Slice into triangles then serve.
To freeze the quesadillas, stack the filled and uncooked quesadillas with a piece of parchment paper between each quesadilla. Place in a freezer bag and freeze for up to three months. To reheat either microwave (for a soft quesadilla) or cook in a skillet on low heat (make sure to use low heat so that the filling has time to thaw and melt before the outside burns).
* I used my homemade taco seasoning here, but you can use a store-bought packet of taco seasoning if needed.