Heat the oven to 425 F / 220 C. Line a sheet pan (33 x 46 cm / 13 x 18 inch) with parchment.

Toss the sweet potato cubes with 2 tbsp olive oil, cumin, smoked paprika, chili powder, salt, and pepper in a large mixing bowl until evenly coated.

Spread the sweet potatoes in a single layer on the sheet pan, giving them space so they roast instead of steam. Roast for 22 to 25 minutes, flipping once halfway, until the edges are caramelized and a fork slides in easily.

While the sweet potatoes roast, heat the remaining 1 tbsp olive oil in a 10-inch skillet over medium heat. Add garlic and cook for 30 seconds until fragrant.

Add black beans and 1 tbsp lime juice, stir, and cook for 4 to 5 minutes until warmed through and slightly thickened. Season with a pinch of salt.

Whisk the sour cream, remaining 1 tbsp lime juice, and lime zest together in a small bowl until smooth.

Warm the tortillas one at a time in a dry skillet over medium heat, about 20 seconds per side, until pliable and lightly charred in spots.

Layer black beans and roasted sweet potatoes onto each tortilla. Top with sliced red onion, cilantro, cotija, and a drizzle of lime crema.

Serve immediately while the tortillas are still warm.