How to Make It
Preheat the oven to 450°F with racks in upper and lower thirds. Line two rimmed baking sheets with foil. Lightly brush the foil with oil.
In a large bowl, toss the sweet potato slices with chili powder, cumin, 2 tablespoons of the olive oil, ½ teaspoon salt, and several grinds black pepper. Divide the slices among the prepared baking sheets in a single layer (the rounds should not overlap). Bake, rotating baking sheets top to bottom halfway through and flipping slices, until potatoes are caramelized and browned in spots, 30 to 35 minutes. Remove from oven and flip again, then combine onto one sheet tray. Preheat the broiler to HIGH.
Meanwhile, combine the avocado, yogurt, lime juice, ½ cup cilantro, and remaining 2 tablespoons oil in a food processor or blender. Pulse until smooth. Season with salt and pepper, to taste.
In a small bowl, toss the black beans with a generous pinch of salt and several grinds black pepper. Scatter over sweet potatoes, and top with cheddar cheese. Broil on top rack until cheese has melted, 2 to 3 minutes. Remove from oven and top with the avocado sauce, pepitas, cotija, radishes, cilantro leaves and tender stems, and a pinch of flaky salt. Serve with lime wedges.