The NY Times Magazine carried this a week or two ago. You remove the seeds from a lemon, chop it coarsely, then grind it up--rind, pith and all--with 2 cups sugar in the processor. Then puree 2 pounds hulled strawberries, combine with the lemon slush, add more lemon juice to taste, and freeze.
I made this over the weekend (with Seascape and Albion berries from Dirty Girl Farm at the SF Ferry Building market) and wasn't happy with the result. I think the main flaw is that the lemon pith gives a bitter undertone that I disliked. There's a reason that instructions for zesting citrus fruit caution against including the white pith; this recipe flouts that warning, and I think it's a mistake. If I do this again I'll use lemon pulp and zest, but not the rind.
(Would this be different with a Meyer lemon, rather than the Eureka I used? Maybe. But the recipe just said "lemon.")