Gently mix together turkey, bread crumbs, egg, onion, Worcestershire sauce, thyme, garlic, rosemary, salt and pepper. Divide into portions (approx. 3 per serving); set aside.
Cut cherry tomatoes in half. Partially scoop out centre of tomato halves with small melon baller. Sandwich a cube of mozzarella between 2 tomato halves and wrap with 1 basil leaf. Roll a portion of turkey mixture around each tomato making sure to enclose properly so cheese doesn’t melt out. Chill for 10 minutes.
Cook pasta according to package directions; drain.
Meanwhile, heat olive oil in large skillet set over medium heat. Cook meatballs in 2 batches for 5 minutes or until browned all over. Transfer to plate. Saute onions for 1 to 2 minutes or until softened. Add strained tomatoes and pepper flakes to skillet; bring to a boil. Reduce heat to medium-low. Simmer for 20 minutes or until cooked through.
Toss pasta with sauce. Serve with meatballs over top. Sprinkle parsely on top.
Serve with freshly grated Parmesan cheese, if desired.
Alternatively, brown meatballs in preheated 425°F (220°C). Arrange on parchment paper lined baking sheet and bake for 15 minutes. Then continue to simmer in sauce until cooked through.