01 - Preheat oven to 425°F. Line a baking tray with parchment paper.
02 - Place tomatoes (cut side up), onion, and garlic on the tray. Drizzle with olive oil, sprinkle with salt, pepper, and oregano. Roast for 25 minutes, until tomatoes are soft and slightly caramelized.
03 - While the vegetables roast, soak breadcrumbs in milk in a large bowl for 5 minutes.
04 - Add ground turkey, egg, Parmesan, parsley, minced garlic, salt, pepper, and thyme to the breadcrumbs. Mix gently with your hands until just combined.
05 - Form the mixture into 16 golf ball-sized meatballs.
06 - Heat 2 tbsp olive oil in a large skillet over medium heat. Brown the meatballs in batches, turning until golden (about 5 minutes). Set aside on a plate.
07 - Transfer roasted vegetables to a blender or food processor. Add sugar (if using). Blend until smooth. Pour sauce into a large, deep skillet or saucepan. Bring to a gentle simmer.
08 - Add meatballs to the sauce. Cover and simmer on low for 15-20 minutes, until meatballs are cooked through.
09 - Stir in fresh basil leaves just before serving.