Preheat oven to 400° F. Line a rimmed baking sheet with a piece of parchment paper for easy clean up.

In large bowl, toss sweet potatoes with olive oil and ground cumin. Season with salt and pepper, to taste. Arrange on prepared baking sheet. Roast 20-25 minutes or until brown and slightly crisp around the edges.

While sweet potatoes roast, heat water, vinegar, salt, and sugar in a small saucepan to a steady simmer.

Place red onion in a glass jar. Pour vinegar mixture over the onions. Cool 10-15 minutes at room temperature and then transfer to refrigerator to chill. (The pickled onions will have best flavor if made in advance).

Meanwhile, combine avocado, sour cream, garlic, and lime juice in a blender. Blend until completely smooth and creamy.

Assemble tacos by spreading a dollop of avocado sauce on each tortilla, followed by roasted sweet potato chunks, black beans, pickled red onion, and fresh parsley. Enjoy!