In a medium saucepan, bring 3 cups of water to a boil over high heat. Add black beans to the water and reduce heat to a simmer. Cover and cook for 1 1/2 hours, or until all water has been absorbed.
Preheat oven to 400 degrees.
In a medium bowl, toss butternut squash with olive oil, salt, pepper and red pepper flakes. Spread squash out on a rimmed baking sheet in an even layer. Roast for 25 to 30 minutes.
When the beans are done cooking, stir in cumin powder, garlic powder and salt and pepper to taste for the black beans. Set aside and keep warm over lowest heat setting.
In a small bowl, whisk together the ingredients for the chipotle sauce. Set aside.
To assemble the tacos, layer butternut squash with black beans, shredded cabbage, sliced avocado, and pineapple. Drizzle over chipotle sauce and garnish with freshly chopped cilantro.