In a medium saucepan, heat vegetable oil over medium heat. Add garlic and cook for 1 minute. (If using garlic powder, omit oil and skip this step).
Add tomatoes, lemon juice, salt, pepper and red pepper flakes, if desired. Cook until heated through, stirring occasionally. For a thicker sauce, cook an extra 10 to 20 minutes to allow more of the liquid to evaporate.