For the casserole:
Cooking spray or olive oil
2 tablespoons olive oil
1 medium yellow onion, diced
2 pounds sweet potatoes, peeled and cut into 1/2-inch cubes
1 (28-ounce) can fire-roasted diced tomatoes, drained of juices
1 (15-ounce) can black beans, drained and rinsed
3 cups shredded smoked mozzarella cheese (about 7 1/2 ounces), divided
1 tablespoon smoked paprika
1 tablespoon kosher salt
2 cloves garlic, minced
For serving:
Plain yogurt
Coarsely chopped fresh cilantro