Beef and Butternut Squash Enchiladas

diced butternut squash

extra virgin olive oil

Kosher salt and freshly ground black pepper

homemade enchilada sauce or 1 30-ounce can store bought

package of 10 8-inch flour tortillas

shredded beef, like my Slow Cooker Mexican Pot Roast

yellow or white onion, diced

shredded mozzarella cheese

Chopped green onion and shredded lettuce for garnish and serving