Add sweet potato in a single layer and cook for 4-5 minutes without stirring until beginning to brown on the first side.
Add the onion and stir. Cook for 4-5 minutes, stirring occasionally, until onion is softened and other sides of sweet potatoes are beginning to brown.
Add black beans, bell pepper, garlic powder, cumin, paprika, black pepper, and salt. Stir to coat everything.
Add water and stir. Reduce heat to medium low and simmer, 7-10 minutes, stirring occasionally, until water is mostly evaporated and sweet potato softens.
Remove from heat and squeeze lime juice on top.
Serve with sliced avocado and chopped cilantro if desired. Stores well in the fridge for up to 4 days. Reheat in the microwave or in a hot pan with a drizzle of oil.
Notes
This is best if served immediately. If you would like to store for later, place in an airtight container in the refrigerator for up to 5 days.Slice and serve the avocado right before serving.