Equipment
* optional
Ingredients
Tomato Base
- 3000 g roma or san marzano tomatoes, washed, cored, and halved lengthwise
- 6 garlic cloves, peeled
- 45 ml extra virgin olive oil
- 10 g kosher salt
Canning Safety
- 60 ml bottled lemon juice
Nutrition (per serving)
Nutrition is estimated per serving. Nutrients without complete source data are omitted.
Full nutrition
- Calories
- 49 kcal
- Protein
- 1 g
- Carbohydrates
- 6 g
- Fat
- 3 g
- Fiber
- 3 g
- Sugar
- 6 g
- Sodium
- 202 mg
- Saturated Fat
- 0 g
- Monounsaturated Fat
- 2 g
- Polyunsaturated Fat
- 0 g
- Potassium
- 362 mg
- Calcium
- 17 mg
- Iron
- 0.4 mg
- Magnesium
- 17 mg
- Phosphorus
- 38 mg
- Zinc
- 0.3 mg
- Vitamin A
- 0 mcg
- Vitamin C
- 21 mg
- Vitamin E
- 0.3 mg
- Vitamin K
- 1 mcg
- Vitamin B6
- 0.0 mg
- Niacin
- 0.0 mg
- Folate
- 0 mcg
- Water
- 3 g
Sources: Aggregated Public Data, USDA FoodData Central
Method
Preheat your oven to 200 degrees Celsius or 400 degrees Fahrenheit. Line two large baking sheets with parchment paper or silicone mats.
In a large bowl, toss the halved tomatoes and garlic cloves with olive oil and kosher salt until evenly coated. Arrange the tomatoes cut-side down on the prepared baking sheets in a single layer.
Roast the tomatoes in the preheated oven for 45 minutes, or until the skins are deeply wrinkled and the edges show slight charring. The tomatoes should be completely soft and collapsed.
Allow the tomatoes to cool slightly on the baking sheets for 10 minutes. Transfer the tomatoes, garlic, and any accumulated roasting juices into a blender and process until completely smooth.
For a silky texture, pass the pureed mixture through a food mill or fine-mesh sieve set over a large bowl to extract the seeds and remaining bits of skin. Discard the solids.
Prepare for canning by ensuring jars are hot and sterilized. Add 15 milliliters of bottled lemon juice into each hot pint jar. Pour the hot tomato puree into the jars, leaving a 1.5-centimeter headspace at the top.
Apply the lids and bands until fingertip-tight. Process the jars in a boiling water bath for 40 minutes. Ensure the water covers the jars by at least 2 to 3 centimeters.
Carefully remove the jars from the water bath and let them rest undisturbed on a towel for 12 to 24 hours. Check seals before storing.
Chef's Notes
- Bottled lemon juice is mandatory over fresh lemon juice for water bath canning because it has a standardized, predictable acidity level. Tomatoes walk the line of safe pH levels, and consistent acid prevents botulism.
- Roasting rather than boiling the tomatoes concentrates their natural sugars through the Maillard reaction, resulting in a significantly richer umami profile that enhances whatever dish you eventually make.
- Do not add additional unacidified vegetables like onions, celery, or bell peppers to this puree before canning, as it will alter the pH and render the mixture unsafe for water bath processing.
- To accurately measure headspace, use a standardized headspace tool or the markings on a canning funnel. Proper headspace ensures a strong vacuum seal during the cooling process.
Storage
Refrigerator: 1 week — If successfully water-bath canned, sealed jars are shelf-stable at room temperature for up to 1 year. Refrigerate only after opening.
Freezer: 6 months — Alternatively, freeze the puree in airtight containers or heavy-duty freezer bags instead of canning.
Troubleshooting
Puree is too watery and thin
Cause: The tomatoes used had a very high water content, or the roasting time was not long enough to evaporate excess moisture
Fix: Transfer the strained puree to a wide saucepan and simmer over medium-low heat until reduced to your desired thickness
Prevention: Select paste tomatoes like Roma or San Marzano, which have lower water content and fewer seeds, or roast for an additional 15 minutes
Jars did not seal after processing
Cause: Food particles on the jar rim prevented a clean contact with the lid, or the bands were tightened too firmly
Fix: Store the unsealed jars in the refrigerator immediately and consume within one week, or re-process with fresh lids within 24 hours
Prevention: Always wipe jar rims thoroughly with a damp paper towel before adding lids, and only tighten bands to fingertip-tight
Cultural Context
The tradition of preserving the late summer tomato harvest, known in Italy as making passata, is a cornerstone of Mediterranean food culture. Historically, entire families would gather at the end of the season to boil, mill, and bottle hundreds of pounds of ripe tomatoes to ensure a supply of sunshine-infused flavor throughout the barren winter months. Adding the roasting technique to this traditional practice modernizes the flavor profile by introducing complex, caramelized notes.
