Preheat the oven to 425°F. Arrange the halved cherry tomatoes on a baking sheet. Toss with 1 tablespoon olive oil, ½ teaspoon Italian seasoning, and ¼ teaspoon salt. Roast for 18–20 minutes until softened, juicy, and lightly caramelized.
Meanwhile, heat the remaining olive oil in a deep skillet over medium-high heat. Add the ground beef and onion and cook until the beef develops dark browned edges and the onion becomes tender.
Add the butter, garlic, remaining Italian seasoning, oregano, smoked paprika, black pepper, remaining salt, and tomato paste. Stir for about 1 minute.
Add the roasted tomatoes and their juices, gently crushing about half into the beef. Pour in the heavy cream and milk, then simmer over low heat for 3–4 minutes until the sauce becomes creamy and orange-red.
Remove from the heat and gradually stir in ¾ cup Parmesan and ½ cup mozzarella until melted.
Cook the capellini in salted boiling water until just al dente, usually 2–4 minutes. Reserve ½ cup pasta water before draining. Gently fold the delicate strands into the beef and roasted tomato cream sauce until fully mixed.
Spoon the remaining sauce over the pasta and scatter with the remaining mozzarella and Parmesan. Cover briefly until melted and finish with fresh basil.