Cost per Serving:
1. Preheat oven to 425ºF. Combine beans, olive oil, scallions, chili powder and 1/2 tsp. salt in a bowl.
2. Mist a baking sheet with cooking spray. Place tortillas on sheet and spoon bean mixture on top. Sprinkle with cheese. Bake until golden and crisp, about 10 minutes.
3. While tostadas are baking, combine mango, onion, lime juice and 1/4 tsp. salt in a bowl. Remove tostadas from oven, spoon mango mixture on top and serve immediately.