Step 1

1 Position a rack in the middle of the oven and preheat to 350 degrees

Step 2

2 In a small saucepan over medium-low heat, combine the beans and water, and warm, stirring with a rubber spatula, until the beans are warm and spreadable, about 3 minutes

Step 3

3 Add more water, 1 tablespoon at a time, if needed

Step 4

4 Remove from the heat

Step 5

5 Place the tostada shells on a large, rimmed baking sheet

Step 6

6 Evenly divide the bean mixture among the shells, spreading into an even layer

Step 7

7 Sprinkle the cheese evenly on top

Step 8

8 Transfer the baking sheet to the oven for about 5 minutes, or until the tostadas are warmed through

Step 9

9 Divide the tostadas among plates and top each with lettuce and avocado

Step 10

10 Drizzle each with crema or sour cream and hot sauce, and serve with a lime wedge, if using

Step 11

11 NOTE: If you do not have crema, you can substitute with sour cream: In a small bowl, whisk together 1/2 cup sour cream and 1 tablespoon each of water and lime juice until well combined