Preheat the oven to 325°. Cut across the tomatoes horizontally, leaving the top half slighter smaller than the bottom to create a lid. Set a strainer over a medium bowl. Using your fingers, scoop the tomato seeds into the strainer; press on the seeds to extract the juice. Using a small spoon or melon baller, scoop out the center of the tomatoes and coarsely chop them. Add the chopped centers to the juice in the bowl. Add the rice, beef, garlic, parsley, basil, 2 teaspoons of kosher salt, 1/4 teaspoon of pepper and 2 1/2 tablespoons of the olive oil and knead to combine.
Set the tomatoes in a large baking dish and season with salt. Spoon the filling into the tomatoes, cover with the lids and drizzle with the remaining 2 1/2 tablespoons of olive oil. Bake for about 1 1/2 hours, basting occasionally, until the tomatoes are soft and the rice is cooked. Let the tomatoes stand for 15 minutes before serving warm or at room temperature.