Crockpot ketchup

1 cup pureed tomatoes
1 small onion, coarsely chopped
1/2 cup lemon juice
1/4 teaspoon ground allspice
1/4 teaspoon ground cinnamon
1/4 teaspoon ground mace
1/4 teaspoon ground ginger
1/4 teaspoon ground cloves
1/4 teaspoon ground red pepper
salt to taste
fresh ground black pepper to taste

Place all ingredients except kosher salt and black pepper into a medium crockpot.
Stir well. Cover and turn on high for 2 – 2 1/2 hours, stirring occasionally. Remove the lid and puree with an immersion blender, or transfer to a regular blender or food processer and puree until smooth. Return to crock (if you used a blender of food processor) and cook on high uncovered for 30 minutes to 1 hour, stirring occasionally, until ketchup has reached desired consistency.