Wash firm unblemished tomatoes. Dip in boiling water for 30 seconds or until skins start to split. Dip in cold water; remove skins and cores.
Place a wide mouth funnel in a hot clean pint or quart canning jar. Ladle whole or halved tomatoes into the jars along with any juices from preparing the tomatoes. Add 1 tablespoon lemon juice to each pint jar or 2 tablespoons lemon juice to each quart jar. Add boiling water, leaving 1/2-inch head space.
Remove funnel; wipe the jar rims and adjust lids. Process full jars in a boiling water canner 40 minutes for pints; 45 minutes for quarts. Begin timing when water returns to boiling. Makes about 7 quarts or 12 to 14 pints (twenty-one 1/2-cup servings).