Warm the oil: Set a medium saucepan over medium heat and add the olive oil. Give it a minute to shimmer.

Sauté aromatics: Add the garlic (and onion if using). Cook 1–2 minutes, stirring often, until fragrant. Do not brown the garlic; if it starts to color, lower the heat.

Build the base: Stir in tomato paste and cook for 30 seconds. This wakes up the flavor and deepens the sauce.

Add tomatoes and spices: Pour in the crushed tomatoes. Add oregano, dried basil, red pepper flakes, bay leaf, salt, and black pepper. Stir to combine.

Simmer gently: Bring to a light simmer, then reduce heat to low. Cook uncovered 15–25 minutes, stirring occasionally. The sauce should thicken slightly and taste more rounded.

Adjust acidity: Taste. If it’s sharp, add 1/2 teaspoon sweetener and the butter. Stir and taste again. Add more sweetener in small amounts until the acidity balances without becoming sweet.

Finish with freshness: Remove the bay leaf. Fold in fresh basil if using. For a smoother sauce, blend with an immersion blender for 5–10 seconds.

Final seasoning: Add more salt and pepper if needed. The sauce should taste bright, savory, and clean.