Wash and cut the tomatoes in half through the center (not top to bottom).
Carefully hollow out the tomato halves by scooping out the pulp. Place the pulp in a large mixing bowl and set the hollowed tomato halves cut-side up on a broiling pan.
Combine kosher salt, black pepper, basil, and mozzarella balls pieces with the tomato pulp. Mix well to combine.
Preheat the broiler.
Brush each hollowed tomato half with olive oil, then fill with the pulp/mozzarella mixture. Use a slotted spoon to drain excess liquid from the mixture while you fill the tomatoes.
Place in the oven about 5 inches from the broiler and cook for 3-4 minutes. Tops brown, the cheese melts and the tomatoes soften when done.
Remove and let cool slightly.
Top with crumbled bacon and serve.