Use store bought tostadas or make your own. To make your own tostadas, preheat the oven to 400 F. Place the tortillas on a baking sheet and mist them with cooking spray or an oil of your choice. Bake for 5 minutes, flip and bake an additional 3 to 5 minutes, until crisp. In a medium bowl, mix together the grapes, jicama, avocado, cilantro, jalapeño, lime zest and juice, and salt. Spread the beans on the tortillas and top them evenly with the salsa mixture. Variations Try black beans instead of refried beans for a healthier option. Purchase tostadas instead of making your own for a quicker meal.