In a large skillet, heat the olive oil over medium heat.
Add the chopped red onion. Sauté for about 3-4 minutes until they start to soften.
Add the diced sweet potatoes and diced red bell pepper to the skillet. Cook for approximately 20 minutes, stirring occasionally, until the sweet potatoes are tender and slightly caramelized.
Stir in the minced garlic, ground cumin, chili powder, smoked paprika (if using), salt, and pepper. Sauté for another minute until fragrant.
Once the sweet potatoes are cooked, add the drained black beans and corn kernels to the skillet. Cook for an additional 5 minutes, stirring occasionally, until the mixture is heated through and the beans are tender.
Squeeze the juice of one lime over the filling and stir to combine. Remove from heat.
Heat the taco-sized tortillas in a dry skillet over medium heat for about 20-30 seconds on each side until they are warm and pliable. Alternatively, you can warm them in the oven or microwave.
Spoon a generous portion of the black bean and sweet potato filling onto each warm tortilla.
Top the filling with sliced avocado or guacamole, salsa or pico de gallo, vegan sour cream or yogurt, and any additional toppings you prefer.
Garnish with chopped fresh cilantro leaves and a squeeze of lime juice.