Use hands to form large balls of dough and place on pan. Pat down to flatten to a little less than ¼ inch high and form a round "tortilla." Repeat until all dough has been shaped.
Place in oven and bake for 20 minutes.
After 20 minutes, turn oven to broil. Broil each side of the tortillas for about 4-5 minutes or until they turn golden and begin to crisp up.
While the tortillas are broiling, saute onion in olive oil in a medium pan on the stove top for about 3 minutes.
Then add beans, chili powder, cumin, garlic powder, salt, pepper, and broth. Stir until beans are cooked through and liquid has cooked out.
Once tortillas are crisp, remove from oven. Place a tortilla on a plate then add the beans and finally your favorite tostada toppings.
Recipe by at http://www.beautifullynutty.com/zucchini-carrot-tostadas/