Trim the ends off the lemon and cut in half. Remove the seeds and chop the lemon into chunks.
Puree the lemon and sugar in a food processor and puree until very smooth, about 1 minute. Transfer to a bowl.
Put the berries in the food processor bowl and puree, then stir into the lemon mixture until blended.
If you want a smoother sorbet without bits of blueberry and lemon, push the mixture through a strainer. Otherwise, pour into your ice cream maker and freeze according to the directions of your machine.
Transfer to a container and store in the freezer until ready to serve.
How to make sorbet without an ice cream maker:
Choose a shallow (less than 1-inch deep) metal pan and freeze it for at least an hour before making the recipe.
Follow the recipe to make the lemon-blueberry puree.
Pour the puree into the pan, cover tightly with plastic wrap and freeze.
Scrape the mixture with a fork every 30 minutes or so to break down the ice crystals, moving the sorbet from the edge to the center each time.
Make other berry-flavored sorbets using an equal amount of strawberries, raspberries or blackberries instead of blueberries.Adapted from a recipe in the Italian Country Cookbook.