Heat a skillet to medium-low and add 1 tsp of oil. Toss in sweet potatoes, chili powder, and a dash of salt and pepper. Cover and cook on medium-low stirring occasionally to prevent burning. When the potatoes are nice and tender and begin to get a light char on them, they are done.
In a small saucepan over low heat; add the black beans, garlic, cumin, lime juice, and a dash of salt & pepper. Cover and cook for about 5 minutes to allow the flavors to develop into the beans.
Now heat a small frying pan over medium-high heat. Heat each tortilla for about 30 seconds on each side and then place them in a warm area while you prepare the remaining tortillas.
Now it's time to pile up those tacos! You know what to do! Fill up your tortillas with all the goodies - beans, sweet potato, spinach, onions, cilantro, and finally a dollop of sour cream. If you want to spice things up - add some of your favorite hot sauce! Enjoy!