Butternut Squash Black Bean Tostadas

For the Tostada Shells:

blue corn tortillas

Cooking spray

Salt

For the Butternut Squash:

medium butternut squash, peeled, seeded and cut into 1/2-inch cubes

olive oil

ground cumin

lime juice

Salt and black pepper,

For the Creamy Avocado Dressing:

ripe avocados, peeled and seeded

low-fat buttermilk

garlic, minced

chopped fresh cilantro

chopped green onion

small jalapeño pepper, chopped and seeds removed

fresh lime juice

ground cumin

Salt and ground black pepper,

Tostada Toppings:

black beans, rinsed, drained, and heated

small red onion, diced

pepitas

Chopped Lettuce