Cook the garlic in the olive oil on medium heat until soft but not browned. Add the juice of once lemon to the garlic and then add the pasta back. Add a 1/2 cup of parmesan and gently stir a few times to coat and melt the cheese, adding a 1/4 cup of the pasta water to thicken the sauce. Add more pasta water a tablespoon at a time if it is too dry. The sauce should be a thin coat around the tortellini. Add salt and pepper to taste. Turn off the heat.