smoky black bean tacos

Name: smoky black bean tacos
Ingredients: 1 15-ounce can black beans, rinsed and drained; 1 small onion, diced; 1/2 red bell pepper, diced; 2 cloves garlic, minced; 1 tablespoon olive oil; 1 teaspoon cumin; 1/2 teaspoon chipotle powder; 1/4 teaspoon kosher salt; 1/4 teaspoon black pepper; 1/4 cup chicken broth; 2 mangoes, peeled, pitted and diced; zest and juice of 1 lime; 1/4 red onion, minced; 1 serrano pepper, seeded and minced; pinch of salt; 4 flour tortillas; 1 avocado, thinly sliced; 1/2 cup each grated or crumbled cheese for sprinkling (such as cheddar, monterey jack or queso fresco); 1/2 cup cilantro; lime wedges for serving