Vegetarian meals do not feel meager when the main ingredient is dense, flavorful butternut squash. The beauty of tostadas is that you can add as many toppings as you please: Sliced avocado, hot sauce or even a drizzle of sour cream would all be welcome additions.
Heat oven to 425 degrees Fahrenheit. Using a sharp chef’s knife, remove stem from butternut squash, then cut long neck from its base. Using a vegetable peeler (a Y peeler works best for this), peel squash and cut base in half. Remove seeds and cut squash into 1-inch cubes (you should have about 6 cups).
Place squash on a baking sheet and toss with oil, salt, chili powder and pepper. Roast until tender, about 20 minutes.
While squash is roasting, make the slaw: In a large bowl, whisk together oil, lime juice, salt, cumin and pepper. Add remaining slaw ingredients and toss until well coated. Taste and add more salt or lime juice if necessary.
When squash is ready, spread some hot refried beans on a tostada shell, then top with roasted squash and a handful of slaw. Sprinkle feta cheese over the top and serve with a lime wedge.