Preheat the oven to 400°F and coat a shallow baking pan with nonstick spray.

Remove the cores from the tomatoes and cut away a very thin slice from both the top and bottom of each to expose the flesh.

Cut each tomato into 3 thick slices (about 5/8-inch) and arrange them on the prepared baking pan.

Combine the olive oil and garlic in a small bowl and brush some onto each slice of tomato, then season with salt and pepper.

Roast until the tomatoes are tender and the skins are slightly wrinkled, 9 to 12 minutes.

Remove from the oven, top with mozzarella, then continue roasting until the cheese is nicely melted, 2 to 3 minutes longer.

Top with the chopped basil and serve immediately.