Preheat oven to 400F. Place tortillas on baking sheet and spray each side with non-stick cooking spray. Bake tortillas 4 minutes on each side or until edges are slightly curled. Remove from oven and set aside.
In a small bowl, add refried beans, chili powder, cumin powder, and lime juice. Mix all ingredients together and microwave for 1 1/2 minutes or until beans are warm.
Assemble tostadas by topping each toasted tortilla with 1/4 cup refried bean mixture, 4 avocado slices, 1/4 cup pico de gallo, 2 Tbsp crumbled queso fresco, and 1 Tbsp black olives.
Serve as is or squeeze a little lime juice over the top of each tostada before serving.
You can find the pico de gallo in the deli section of your grocery store and the Mexican cheeses in the refrigerated cheese section.