1 Tbsp. olive oil
½ cup chopped onion
¼ cup balsamic vinegar
2 can (14.5oz.each) Del Monte® No Salt Added Diced Tomatoes, not drained
1 can (8oz.) Del Monte® Tomato Sauce
½ tsp dried rosemary [or 1 1/2 tsp. chopped fresh rosemary]
1 lb. frozen pre-cooked beef or turkey meatballs
Slider buns, 1 to 2 dozen (1 bun per meatball)
Provolone cheese, sliced, cut into quarters
Heat olive oil in a deep 12-inch skillet over medium heat. Add onion and cook 2 minutes or until lightly browned. Stir in vinegar; simmer 1 minute until almost evaporated. Add diced tomatoes, tomato sauce and rosemary; bring to a simmer.
Add meatballs and return to a simmer. Cook, uncovered, 15 minutes, stirring occasionally, or until meatballs are heated through and sauce is slightly thickened. Season to taste with salt and pepper.
Place meatballs and sauce on bun bottoms. Top meatballs with cheese quarters and then bun tops.