Saute the onions, carrots, sweet potatoes in olive oil over medium heat. Add in the garlic, chili powder, cumin, paprika, salt, and cayenne if you’re using it.
While the veggies are cooking, chop your cilantro and set aside. Prepare your Greek yogurt sauce. Empty the yogurt into a bowl, and stir in 2 tsp of taco seasoning.
Begin assembling your tacos! Heat up your corn tortillas, and on each tortilla put: 2-3 Tbsp refried black beans, 1/3 cup of the veggie mixture, 1-3 Tbsp of the yogurt mixture.