01 - Preheat oven to 400°F for roasting the zucchini boats.
02 - Halve zucchini lengthwise. Use a spoon to scoop out the flesh, leaving a ¼-inch thick shell. Reserve ½ cup of the scooped flesh and chop it finely.
03 - Place zucchini boats cut side up on a baking sheet. Brush with 1 tablespoon olive oil and season with salt and pepper. Roast for 15 minutes.
04 - Heat remaining 1 tablespoon olive oil in a large skillet over medium heat. Add onion and sauté for 2 minutes until softened. Add garlic, chopped zucchini flesh, and butternut squash; cook for 8-10 minutes until squash is just tender.
05 - Stir in black beans, chili powder, cumin, smoked paprika, and ¾ cup enchilada sauce. Cook for 2-3 minutes to meld flavors, then remove from heat.
06 - Remove zucchini boats from oven. Spoon the black bean and squash mixture evenly into each boat, packing gently.
07 - Drizzle remaining ¾ cup enchilada sauce over stuffed boats and sprinkle with shredded cheese.
08 - Return to oven and bake for 15-20 minutes until cheese is melted and bubbly and zucchini is fork-tender.
09 - Top with queso fresco, cilantro, avocado slices, and lime wedges as desired. Serve hot.