How to Make It
Core tomatoes with a paring knife, and score the bottom of each tomato with an “X,” cutting just through the skin but not into the flesh. Place 5 or 6 tomatoes in a large pot of boiling water for 30 seconds. Remove tomatoes with a slotted spoon, and immediately plunge into a large bowl of ice water to stop the cooking process. Remove tomatoes to a large rimmed baking sheet lined with paper towels. Repeat procedure with remaining tomatoes. Peel and discard skins from tomatoes, and coarsely chop.
Process tomatoes, in batches, in a food processor until blended and smooth, 1 to 2 minutes (for a chunkier sauce, do not process until completely smooth). Transfer each batch to a 10-quart stockpot.
Bring processed tomatoes and salt to a boil over medium-high; reduce heat to medium, and simmer, stirring occasionally, until reduced by half or to desired consistency, 2 to 2 1/2 hours.
Place 1/4 teaspoon citric acid in each hot, sterilized jar. Ladle mixture into jars, leaving 1/2-inch headspace. Remove air bubbles. Wipe jar rims. Center lids on jars, apply bands, and adjust to fingertip-tight. Place jars in boiling-water canner. Process as directed for 35 minutes.