Preheat oven to 350˚F. Line two sheet pans with foil or parchment paper. Place tostada shells on sheet pans and set aside.
Drain beans and place in a bowl. Mash with a fork until a little chunky or smooth — whichever you prefer. Set aside.
In a medium sauté pan, heat oil over medium heat until shimmering. Add frozen onion and pepper blend and cook until heated through, about 3-5 minutes. Remove from heat.
Top each tostada with mashed beans and cooked onions and peppers.
Place in the oven for about 12 minutes, or until tostadas are heated through.
Top with your favorite toppings like sliced avocado, salsa, diced tomatoes, sour cream, guacamole, tortilla strips or shredded cheese. Serve immediately.
Video
Notes
For extra protein, add shredded or ground chicken, ground turkey or pulled pork.