In a large bowl toss together tomato halves along with fresh thyme, 1 tsp of salt and 1/4 cup olive oil. Arrange tomatoes on a large baking sheet cut side up.
In the same bowl, use your hands to combine the ground chicken, remaining salt, eggs, fennel, parmesan cheese, garlic and bread crumbs.
Using your hands form uniform meatballs about 2 tbsp each. Arrange the meatballs on the same baking sheet between tomato halves.
Roast meatballs and tomatoes on center rack for about 30 minutes or until tomatoes begin to soften and are slightly browned. Turn heat up to 500°F and brush meatballs with olive oil. Cook for another 5 minutes.
Once tomatoes and meatballs are roasted toss them together with cooked spaghetti, ¼ cup of olive oil, fresh basil and freshly grated parmesan cheese.