Preheat the oven to 400ºF and lightly spray a rectangle baking dish with cooking oil spray.
To prepare the tomatoes, cut the tops off of each and set aside. Use a spoon to scoop out the inside flesh and place it into a bowl. Season with garlic salt, and pepper, and add in the mozzarella, parmesan, and basil.
Arrange the tomato shells into your prepared baking dish. Fill each with the cheese mixture.
Bake for 10-12 minutes, then cover with the reserved tops and continue to bake for 2-4 minutes.
Notes
Store in an airtight container in the refrigerator for up to 4 days. Reheat in the microwave until the tomatoes are just warmed through. I do not recommend freezing these tomatoes.