Simple Tomato Sauce

In a medium saucepan, heat olive oil over medium-high. Add garlic; cook until fragrant, about 1 minute. Add red-pepper flakes (optional) and tomatoes, breaking them up as you go. Season with salt and pepper. Bring to a boil, then reduce to a rapid simmer. Cook, stirring often, until sauce thickens, about 15 minutes. Stir in oregano leaves.