PRESERVED ROASTED TOMATO PURéE

Steps:

• Heat oven to 325 degrees. Core and halve tomatoes and scoop out seeds and gel. Pile tomatoes into a large roasting pan, or on 2 sheet pans, cut side up. Do not add oil.
• Roast tomatoes for 2 hours. Thoroughly purée tomatoes using a blender or immersion blender. It should be smooth and velvety, with no pieces.
• Put a rack in a large stockpot or line pot with a folded kitchen towel, then fill pot with water and bring to a boil. Add pint jars and boil for 10 minutes. Jars may be left in warm water until ready to fill. Alternatively, sterilize jars by running them through a dishwasher cycle, keeping them warm in the machine.
• Place canning rings in a small saucepan, cover with water and bring to a boil. Turn off heat and add flat lids to soften their rubber gaskets. Rings and lids may be left in water until jars are filled.
• In a nonreactive pan, bring purée to a brisk boil for 5 minutes. Ladle hot tomato purée into warm jars leaving 1/2 inch head space, plus room to accommodate lemon juice. If using citric acid, fill to 1/2 inch head space.
• Into every pint jar, add one tablespoon lemon juice or 1/4 teaspoon citric acid. If using salt, add 1/2 teaspoon to each pint jar.
• Wipe jar rims clean with a damp towel. Place lids on jars, screw on rings and lower jars upright into boiling water. Return to a full boil and process for 35 minutes. Transfer jars to a folded towel and let cool for 12 hours. Jars will ping as they seal. Once cool, test seals by removing rings and lifting jars by flat lids. If a lid releases, the seal has not formed. Unsealed jars should be refrigerated and used within three days or reprocessed. Rings and jars may be reused, but a new flat lid must be used each time.