Step 1

Prepare Jalapeño-Feta Sauce: To a blender, combine mayonnaise, feta, pickled jalapeños and brine, lime juice, and taco seasoning; blend until smooth. Transfer to a bowl or glass jar.

Step 2

Prepare black bean mixture: Heat olive oil in a large skillet over medium. Add onion; cook 4 to 5 minutes, until soft. Stir in chipotle chiles, cumin, and garlic powder.Add black beans, broth, and salt; bring mixture to a simmer. Use a spatula, wooden spoon, or potato masher to partially mash the black beans, binding everything together. Continue simmering until mixture thickens, about 5 to 6 minutes. Stir in lime juice; taste and adjust seasonings as needed.

Step 3

Assemble tostadas: Spread black bean mixture evenly on tostada shells. Top evenly with chunks of avocado, minced red onion (optional), a drizzle of jalapeño-feta sauce, additional crumbled feta, and fresh cilantro.