Preheat your oven to 400°F (200°C). Place the whole garlic cloves on a small baking sheet, drizzle with a teaspoon of olive oil, and roast until golden and fragrant, about 20 minutes.
While the garlic roasts, chop the ripe tomatoes into halves or quarters, and set aside.
Heat a tablespoon of olive oil in a saucepan over medium heat. Add diced onion if using, and cook until translucent and fragrant, about 3-4 minutes.
Add the chopped tomatoes to the saucepan and stir well. Let them cook down for 10-15 minutes, breaking them apart with a spoon until they release their juices and start to thicken.
Remove the roasted garlic from the oven once fragrant and slightly caramelized. Squeeze the soft roasted garlic out of its skins into the sauce, stirring to combine.
Mix in the aged balsamic vinegar for a touch of sweetness and depth. Season with salt and pepper to taste, and simmer the sauce for another 5-10 minutes to meld flavors.
Once the sauce has thickened to your desired consistency, taste and adjust seasoning if needed. It should be vibrant, fragrant, and slightly glossy.
Serve hot over cooked pasta or use as a flavorful base for other dishes, enjoying the rich, caramelized flavors in every spoonful.
