Wash the tomatoes thoroughly and cut a shallow "X" on the bottom of each tomato.

Bring a large pot of water to a boil and carefully lower the tomatoes into the boiling water using a slotted spoon.

Blanch the tomatoes for 1-2 minutes or until the skin starts to peel off. Remove them and plunge them into a bowl of ice water to stop the cooking process.

Once cooled, peel the skin off the tomatoes and discard. Cut the tomatoes in half and remove the seeds.

In a large saucepan, heat the olive oil over medium heat. Add the minced garlic and chopped onion, sautéing until softened and fragrant.

Add the prepared tomatoes, basil, sugar (if using), salt, and pepper. Stir well and bring the mixture to a gentle simmer.

Reduce the heat to low and let the sauce simmer uncovered for about 1 to 1.5 hours, stirring occasionally. The sauce should thicken and intensify in flavor.

Once the sauce reaches the desired consistency, remove it from the heat and let it cool slightly.

Using a blender or food processor, puree the sauce until smooth and velvety. For a chunkier texture, pulse the sauce a few times to leave some tomato bits intact.

Allow the passata to cool completely before transferring it to sterilized glass jars. Store in the refrigerator for up to one week or freeze for long-term storage.