Sweet Potato Tostadas

I love a combination of sweet and spicy, so these layered Sweet Potato Tostadas fit the bill. Also, this is a great meal to make that allows your family members or friends choose their own toppings!
Serves 4.

8-10 Corn tortillas*
2 cans of fat-free refried beans (we used Trader Joe's), warmed in microwave
4 baked sweet potatoes (these can be made ahead of time and warmed just before you eat)
Frozen organic corn, defrosted (we used Trader Joe's)
2 tomatoes, chopped
Lettuce, chopped
Salsa (we used our homemade Salsa Fresca)
Mashed avocado (optional)

* To bake your own OIL-FREE tostada shell/base, preheat oven to 350 degrees. Place tortillas directly on rack and bake for 13-16 minutes, until lightly brown, watching them closely so they don't burn. Test to see if they are done by pinching off the edge of one. If it's crispy, they're ready!