Coat 1.5 quart baking dish with cooking spray and pre-heat oven to 350 degrees.
In small skillet, sauté red pepper and onion with garlic and vegetable broth until tender 3 - 5 minutes. Place in bowl.
Drain beans, reserving 2 Tblsp of aquafaba from beans. Rinse beans well. Place in bowl with sautéed vegetables along with taco seasoning and favorite salsa.
Crumble 3 tostadas and place in bottom of dish. Top with 1/2 of bean mixture, 2 Tblsp cheesy sauce and 1/2 cup spinach. Crumble another 3 tostadas on top of spinach. Add remaining bean mixture and 2 Tblsp cheesy sauce. Crumble remaining 3 tostadas on top.
Bake in oven for 30 minutes.
Top with your favorite ingredients and drizzle with additional cashew cheesy sauce.