For muhammara: Add roasted peppers to reserved skillet; stir 1 minute. Add 1/2 cup water and 2 tablespoons pomegranate molasses. Bring to simmer, scraping up browned bits. Cook until reduced to 2/3 cup, stirring occasionally, about 4 minutes. Mix in parsley. Season to taste with salt, pepper, and more pomegranate molasses, if desired. Transfer to small bowl.
Arrange onions and meatballs on platter. Serve with warm breads, yogurt sauce, and muhammara.