Preheat oven to 400ºF.
Toss the potato cubes, onion wedges, olive oil, lime juice, cumin, chili powder, and salt in a bowl. Transfer to a rimmed baking sheet with parchment paper and bake for about 25 minutes, or until potatoes are tender, stirring halfway through cooking time. When there is about 10 min to go, wrap your tortillas and put them in to warm them up.
When potatoes are almost done, combine the black beans and salsa in a small saucepan. Cook over medium heat until warmed through.
Fill each taco with salsa beans and sweet potatoes, then finish with desired toppings and a squeeze of lime juice. We used a few dollops of sour cream and cilantro as extra toppings