Butter a 10 inch springform pan. For the crust, combine the cookies and sugar in a food processor and process into crumbs. Pour into a medium bowl and stir in the butter. Spread the crumbs evenly and firmly over the bottom and sides of the prepared pan. Bake for 8 minutes, or until golden and crisp. Remove from the oven and let cool completely on a wire rack.
In a food processor, process the ricotta cheese on high speed until smooth and creamy. Add the sour cream, cream cheese, egg, egg whites, sugar, rice flour, xanthan gum, vanilla, lemon zest and salt. Process until blended, then pour into the prepared crust.
Bake at 325°F until the center is set, 45-50 minutes.