Preheat oven to medium heat on grill setting. Place the cherry tomatoes on an oven tray lined with foil. Drizzle with olive oil, and bake until cooked through (approximately 10 minutes)
Put a large pot of salted water to boil; Meanwhile, heat a Tbsp. of olive oil in a deep pan; add the chopped onion, minced garlic and crushed chili and gently fry for around 5 minutes on low heat until soft without color. Add the tomato pulp with ½ cup water and allow to simmer for 20 minutes. Add the roasted cherry tomatoes, some torn basil leaves and stir.
Add your pasta to the pot of boiling water, and cook until al dente. Once cooked drain and place pasta in an ovenproof casserole dish. Add the tomato sauce and half the parmesan cheese and mix until sauce is evenly incorporated. Chop the mozzarella balls and scatter them on top with the remaining parmesan cheese and fresh basil leaves.
Bake in the preheated oven for 10-15 minutes, or until the top is golden and the cheese has fully melted.