Preheat oven to 425 degrees F.
Make the meatballs by combining the turkey with panko, cilantro, egg, milk, grated onion, garlic, paprika, cumin, coriander, salt, and pepper until well combined. Form the mixture into 12 medium meatballs and place them on a baking sheet. Bake the meatballs for 10 minutes. Remove from the oven and set aside.
Meanwhile, make the tomato sauce. Heat 1 tablespoon oil in a large pan over medium heat. Saute the garlic until aromatic and lightly browned, about 1 minute. Add the canned tomato, red wine, chipotle and adobo juices, paprika, cumin, oregano, and sugar. Cover the pot and bring to a simmer. Reduce heat to low and continue to simmer for 10 minutes. Season the sauce with salt and pepper.
Add the meatballs to the sauce. Cover the pot and continue to simmer on low for 20 minutes.
Heat 1 tablespoon oil in a large saute pan over medium heat. Saute the red bell pepper and onion until softened and lightly charred, about 7-8 minutes. Remove from heat and keep warm.
Assemble the sandwiches. Split open the sandwich bread and fill each with 3 meatballs with some sauce. Top with the charred peppers and onion and sliced mozzarella on top. Lay the sandwiches on a baking sheet and bake in the oven for 2-3 minutes or until the cheese is melted. Serve immediately with extra sauce on the side.