Step 1

Make the pickled onions: In a medium bowl, combine the sliced onions with the lime juice, vinegar and salt and stir until the onions are well coated. Let the onions sit while you make the slaw and tostadas. The pickled onions can be stored in a jar in the fridge for up to 1 week.

Step 2

Make the slaw: In a large bowl, combine the cabbage, cilantro, jicama, lime juice, cumin and chili powder. Season with salt and pepper to taste, and set aside.

Step 3

Assemble the tostadas: Preheat the oven to 425 degrees Fahrenheit. Brush or spray both sides of each tortilla generously with olive oil or cooking spray, season with salt, and arrange in a single layer on a large baking sheet. Bake for 4 minutes, then flip and bake for 4 to 8 more minutes, until the tortillas are crispy.

Step 4

Gently heat the refried beans in the microwave or on the stovetop. In a large bowl, mash the avocados with a fork or potato masher. Stir in the lime juice and season with salt, to taste.

Step 5

Spread refried beans evenly over each tortilla. Add a layer of smashed avocado and top with the slaw, pickled onions, tomatoes and queso fresco. Serve immediately.