If you're going to can this recipe, sterilize the jars according to standard procedure.
Rough chop the green tomatoes and ginger, just so they will fit into a food processor or blender. Process or blend into a puree.
Pour the puree and sugar into a large pot over medium-high heat. Add the lemon zest and juice, cinnamon, and allspice and salt well.
Bring to a low boil, and simmer steadily for 30 min to an hour. It should be thick and the flavor should be well blended. Season to taste with salt and lemon juice. Add additional spices, if you like.
The jam is now done. If you prefer to can, take the mixture to 220 degrees and ladle into sterile jars. Wipe rims clean, and place lids and rings on the jars. Place in hot water, making sure the jars are fully covered and process for 10 minutes.
Remove and place on countertop... you may hear a pop as they seal. Tighten the seals after cooling. Any jars that do not seal need to be used immediately and kept in the refrigerator.
Give to friends and family! Enjoy!