Boil a large pot of water over high heat and once it's boiling remove it from the heat.
Add the whole tomatoes one by one and after about 30 seconds remove the tomatoes and plunge them into a bowl of cold water.
Peel the skin from the tomatoes (this should be easy to do after blanching them as directed above).
Repeat this blanching process with the peaches and pears.
Chop the tomatoes, peaches and pears (removing the pits and cores from the fruit) into 3/4-inch pieces and add them to a very large pot.
Chop the onions finely, along with the red peppers, and add them both to the pot as well.
Pour the vinegar into the pot and add the cinnamon, salt and allspice to a piece of cheesecloth and tie it up into a little sachet with a piece of string. Add the sachet to the pot.
Stir everything together well and set the pot on the stove over medium heat.
Let the mixture boil gently for about 2 hours, uncovered, stirring regularly and reducing the heat as necessary.
After 2 hours, add the sugar and stir well.
Continue boiling for one more hour until the mixture thickens. Stir regularly and keep the heat as low as possible to prevent burning (but be sure the mixture continues to boil slowly). Remove the sachet of spices and discard.
Sterilize your jars and lids according to proper canning procedures.
Add the mixture to the jars leaving about 1/2 inch of room at the top of each jar. Add the lids.
Process the filled jars in a pot of boiling water for at least 5 minutes (you may need a rack at the bottom of the pot to prevent the jars from sitting on the bottom of the pot where they may crack or break).
When the jars have finished processing, remove them to a wooden board to cool completely. Any lids that have not popped down (indicating a proper seal) should be stored in the fridge and consumed within 1.5 months.
Properly sealed jars can be stored at room temperature in a cool, dark place for up to one year.