Preheat oven to 400° Fahrenheit. Line baking sheet with paper towels.
Place tomatoes on cutting board and slice in half horizontally (like a hamburger bun). Scoop out pulp and seeds, then lightly salt insides and place cut-side-down on baking sheet. Let juices drain, approximately 15 minutes.
While tomatoes drain, mix together breadcrumbs, garlic, chopped basil, ½ teaspoon salt, black pepper, parmesan, mozzarella, and oil to create filling. Stir until thoroughly combined.
Turn tomatoes over, with open-side facing up. Portion equal amounts of filling into tomatoes. Fill each tomato to the brim, then press down on filling to gently compress. Pile remaining filling on top of each tomato and form into small mound.
Place filled tomatoes in baking dish. Transfer to oven and bake approximately 15 minutes, until tomatoes are cooked through. Tops of filling should be golden brown. Note: be careful not to over-bake.
Remove tomatoes from oven. Garnish with small amount of extra fresh basil and serve.