Preheat the oven to 400 degrees F.
Put the beef bone on a rimmed baking sheet and roast for 30 minutes. Set aside.
Drizzle 3 tablespoons of the olive oil on a separate rimmed baking sheet. Add the tomatoes cut-side down in a single layer. Drizzle the tops of the tomatoes with an additional 3 tablespoons olive oil, sprinkle with 2 teaspoons salt and 1 teaspoon pepper and add the parsley. Roast until tender, 25 to 40 minutes. Transfer the tomatoes and parsley to a blender and puree until smooth. Set aside.
Heat a large stockpot on high heat and add the remaining 3 tablespoons olive oil. Add the garlic and saute for 1 minute. DO NOT let the garlic burn. Add the reserved tomato puree and bone to the pot. Simmer for 45 minutes to 1 hour, stirring occasionally. Season with additional salt and pepper.