Finely chop the tomatoes and place them, along with any liquid on the cutting board, into a bowl. Bring a large pot of lightly salted water to a boil. In the meantime, add the oil to a large skillet that has been set over medium heat. Add the garlic and cook 1 minute. Add the tomatoes and bring them to a simmer. Simmer until they just begin to soften and break up into a chunky sauce, about 5 minutes. Season with salt and pepper and keep warm over low heat. Boil the ravioli until tender, about 3 to 4 minutes. Reserve 1/2 cup of the cooking liquid before draining well. Add the ravioli, reserved cooking liquid, and basil to the sauce and toss to coat. If desired, sprinkle with Parmesan cheese before serving.