Notes
Any whole tomatoes will work in this keto marinara sauce, however, San Marzano tomatoes are the best choice.
Method
Choose the tomatoes: Choose ripe, firm tomatoes for the best flavor. Boil water: Bring a large pot of water to a boil. Score the tomatoes: Using a knife, cut a small "X" on the bottom (blossom end) of each tomato. This helps peel the skin easily. Prepare ice water: Fill a large bowl with ice water. Blanch the tomatoes: Place the tomatoes in the boiling water, a few at a time to avoid overcrowding. Cook briefly: Boil the tomatoes for 30 to 60 seconds or until the skin starts peeling at the "X". Shock in ice water: Quickly transfer the tomatoes to the ice water with a slotted spoon. Let them cool. Peel the tomatoes: Remove from ice water and peel the skins starting from the "X". Discard the skins. Remove the core: Cut out the tough stem core from each tomato. Blend: Place the peeled tomatoes in a blender or food processor and pulse until smooth. Sauté aromatics: Heat 2 tablespoons of olive oil in a medium saucepan over medium heat. Add the chopped onion and cook, stirring often, until soft and golden (about 5 minutes). Add the minced garlic and sauté for 1 minute, until fragrant. Simmer the sauce: Stir in the blended tomatoes, tomato paste (optional), oregano, salt, and pepper. Simmer for 20–30 minutes, until reduced and thickened. Finish with herbs: Stir in 1 tablespoon of chopped fresh basil if using immediately. Turn off the heat. Cool and store: Let the sauce cool. Transfer to an airtight jar and drizzle a bit of olive oil on top as a preservative. Refrigerating: Store the marinara sauce in an airtight jar in the fridge for 5–7 days. Freezing: Freeze in freezer-safe containers or bags for up to 3 months.