Using paring knife, core stem ends of tomatoes. Cut and "X" across non-stem ends. In large pot of boiling water, cook until skins begin to pull away from flesh, about 30 seconds; transfer to ice water bath. Discard skins, then quarter tomatoes. In fine-mesh strainer set over bowl, press on flesh to extract seeds. In large nonreactive pot, bring tomatoes, lemon juice and salt to boil over high heat. Ladle hot mixture into 5 hot, sterilized 1-pt. jars, leaving 1/2 inch headspace; seal. In water-bath canner, process jars for 35 minutes.