Chop half of the red bell pepper into 1/2" pieces and set aside.. Mince (fine dice 1/4") the other half of the bell pepper and set aside.
Heat oil in a medium saucepan over medium high heat. Add onion, larger, chopped bell pepper, and garlic and sauté for 2-3 minutes until softened and slightly translucent. Add the black beans, cumin, chipotle powder, salt and pepper. Stir to combine. Add the chicken broth and cook over medium heat for 3-4 minutes until most of the liquid is evaporated. Cover and set aside.
In a small bowl combine the mango, the minced bell pepper, red onion, serrano pepper, lime zest and juice and pinch of salt. Stir to combine and set aside.
Heat tortillas. If you have a gas stove, turn the flame on medium and place the tortilla directly on the grate. Heat the tortilla until it starts to puff and char slightly. Use tongs to flip the tortilla. Repeat with the rest of the rest of the tortillas.
Spoon the black beans into the tortilla shell. Tuck in a few slices of avocado. Sprinkle with cheeses, top with mango salsa, fresh cilantro and a squeeze of lime. Enjoy.