Place tomatoes, onion, sugar, vinegar, ginger, salt, allspice and black pepper into a heavy-bottomed Dutch oven set over medium heat. Bring to boil, stirring constantly.
Simmer, stirring frequently, for 1 1/2 to 2 hours or until jam-like consistency and thick.
Cool completely. Transfer to freezer safe containers. Freeze for up to 1 month.