Preheat the oven to 400 degrees. Line a baking sheet with parchment paper
Take the red onion and slice it in half, from root to stem. Then, slice the onion lengthwise (from root to stem) into 1 inch slices. Do not shred them apart, but rather keep the layers in tact. Using your hands or a brush, line both sides with olive oil and place on the side of the sheet tray.
Mix the sweet potatoes, olive oil, and all the sweet potato spices together and add to the sheet tray with the onions. Roast for 30 minutes, or until the onions are toasted but not burnt, and the sweet potatoes are soft enough to be poked by a fork.1 teaspoon ground cuminLower the oven to 350 degrees. While the sweet potatoes and onions are roasting, make the black beans. Saute the chopped white onion over medium heat for about 5 minutes, then add the garlic and cook for another 3 minutes. Add the black beans and all the black bean spices to the pan and cook together for about 5-6 minutes. Taste and adjust to your preferences. Option to press down some beans for a more mushy texture. When done, add to a large bowl.
When the sweet potatoes and onions are done, remove from oven. Toss them together. Add to the bowl with the black beans and combine evenly.
Option to stop here and just scoop the filling into tortillas and enjoy.
Otherwise… on another sheet tray, lightly oil the bottom of the tray. Lightly brush one side of the tortillas on the oil, then fill the other side with the sweet potato black bean mixture and shredded cheese. Fold the tacos over and bake for about 10 minutes to get a crispy shell. Note: If you are having trouble keeping the tortilla down, just bake them for a couple minutes then take out and press down, then return to the oven to get crispy.