Preheat oven to 375° F. Toss sweet potato cubes with a drizzle of olive oil and half of the chili powder and cumin, and a pinch of salt. Roast in the oven for 25 – 30 minutes until the sweet potato are cooked through and golden.
Meanwhile, heat a tablespoon of oil in a medium pan and add onion, peppers, and a pinch of salt; cook 5 – 8 minutes until cooked through. Add the beans and remaining spices and cook until warmed through. Stir in the cooked sweet potatoes.
Warm the corn tortillas by placing them in a dry skillet for 10 seconds on each side over medium high heat.
Assemble tacos by putting a generous spoonful of avocado smash on each tortilla and topping with the sweet potato and bean mixture. Top with scallions, tomatoes, additional cilantro, a lime squeeze and hot sauce, if desired.
Mash the avocados in a bowl and stir in the jalapeño, cilantro and lime juice.