Fill a large bowl with ice cubes and cold water, and set aside.

Slice an "x"in the bottom of each tomato. Bring a large pot of water to a boil, then submerge the tomatoes in boiling water for just 30 seconds. With a slotted spoon, transfer to the ice water bath for a minute or two to stop the cooking. Drain, then peel the tomatoes with a paring knife. Slice in half cross-wise.

Place a wire-mesh strainer over a bowl. Gently squeeze the tomatoes over the strainer until you have 1 cup of juice. Set the juice aside, and discard seeds. Trim stems from tomatoes, then coarsely chop the tomatoes. You should have roughly 6 cups of chopped tomatoes.

Combine the reserved 1 cup of tomato juice with the 6 cups of chopped tomatoes in a large stainless steel or enamel pot. Stir in the sugar, lime juice, garlic, ginger, and lemon verbena sprig, and bring to a rolling boil. Reduce heat to medium low, and simmer for 5 minutes, stirring ocasionally. Discard the sprig of lemon verbena. Simmer for 1 hour, stirring often, until the mixture has thickened. 

Remove from heat, and ladle the jam into clean jars. Allow to sit at room temperature for 1 hour. Cover tightly, then store in refrigerator for up to 3 weeks.