Dolma Mahshi (Iraqi Stuffed Onions)

Make the stuffing: Combine rice, parsley, oil, cilantro, pomegranate molasses, tomato paste, cumin, coriander, curry powder, salt and pepper, and 1 ½ cups water in a bowl; let sit until the rice begins to soak up some of the liquid, about 30 minutes.
Meanwhile, trim the tops and bottoms from onions and peel outer layer; place in a 6-qt. saucepan and cover with water. Bring to a boil over medium-high heat, and cook until onions are tender to the core, about 30 minutes; drain and let cool.
Cut each onion halfway around the side and peel off each whole layer to get about 4 to 5 large layers each. Stuff each layer with 2 tbsp. stuffing and roll up into a football-shaped roll; place rolls in a single layer in a 9″ x 13″ baking dish. Pour stock and tomatoes over rolls and sprinkle with sumac; season with salt and pepper.
Heat oven to 375°. Bake until filling is cooked through and sauce is reduced around rolls, about 1 hour. Divide rolls among serving plates and sprinkle with more sumac; serve with the yogurt.