Step 1

In a small bowl, combine the black beans with 1 tablespoon of lime juice, ¼ to ½ teaspoon chili powder, and ¼ teaspoon salt.

Step 2

Make the spicy mayo: In a small bowl, stir together the mayonnaise and the sriracha.

Step 3

Toss the cabbage with a squeeze of lime (1 teaspoon or so) and a few pinches of salt.

Step 4

Fill each tortilla with the cabbage, avocado slices, black beans, mango, cilantro, the spicy mayo, and feta cheese. For spicier tacos, serve with sliced serrano peppers and extra sriracha. Serve with lime slices on the side.