Preheat oven to 400 degrees F. In a medium bowl add the grape tomatoes and 3 garlic cloves. Drizzle with 3 tablespoons of olive oil and sprinkle with salt, pepper.
In a 9 by 13-inch glass baking dish, place the tomatoes and garlic cloves, ensuring they are in just 1 layer. Roast for 20 minutes, and then stir. Add 2 to 3 tablespoons of hot water, if too dry in appearance. Return to the oven and cook for 20 to 30 more minutes.
When ready, the tomatoes will have begun to shrivel and the liquid in the dish should have thickened. Serve hot from oven.