Preheat the oven to 425°F and line a baking sheet with parchment paper. Slice the squash in half lengthwise, scoop out the seeds and slice into ½-inch segments. Toss the squash slices with a drizzle of olive oil, pinches of salt and pepper, and roast until tender and golden brown, about 30 minutes.

Heat 1 tablespoon of olive oil in a medium skillet over medium heat. Add the onion slices and cook until soft and browned, 3-4 minutes, stirring occasionally. Add the mushrooms, and cook until they are soft and browned, about 5-8 more minutes, stirring occasionally. Season with salt and pepper and red pepper flakes

Assemble the tacos with the onion/mushroom/ mixture and roasted squash. Top with avocado slices, pico de gallo and cilantro with extra lime wedges on the side