Combine all ingredients in a slow cooker set to low heat.
Cover and allow to warm for two hours.
After two hours, remove lid and process with an immersion blender until smooth. Alternately, you can puree the tomato mixture in a blender or food processor in small batches.
Place a lid only askew over slow cooker so that moisture may escape. Continue to cook and reduce the mixture on low heat for approximately 18 hours or until desired consistency is achieved.
Ladle into sterilized pint jars, leaving 1/2" headspace.
Wipe rims and place prepared lids and rings on finger tight.
Process in a water bath canner for 15 minutes at a full boil.
Remove from canner and allow to cool, undisturbed for 24 hours. Check for seal and store in a cool, dark place for up to a year. Refrigerate after opening.