Homemade Ketchup

First peel your tomatoes. Have a boiling pot of water, slash a small X on the bottom of each tomato and drop into the boiling water for about 60 seconds. Remove and plunge into cold water and then the skins should easily peel off. If not, return to the boiling water for a few seconds.
Chop roughly and simmer the tomatoes with the onion for 30 minutes. Blend together using an immersion blender(this will not remove the seeds) or put through a food mill. Put the whole spices, cinnamon, cloves and the garlic cloves into a pot with the vinegar. Simmer 30 minutes. Remove the spices.
Meanwhile, boil the tomatoes till reduced by half, stirring frequently. Add the spiced vinegar(I pour it through a strainer to remove the spices), brown sugar, salt, paprika, mustard powder, and all spice. Boil over medium high for 20 minutes till thickened.
To can, pour the mixture into sterilized jars leaving 1/4" headspace. Put the lids on and process for 5 minutes in a boiling water bath. Should yield about 2-3 pints. I assume that you would be able to freeze this as well, making sure to cool completely before freezing, and stirring well after it's thawed to mix back in any water that has separated.

Process and original recipe from Stocking Up by Carol Hupping Stoner under the title Catsup.