Preheat oven to 325. Roll zwieback fine, mix with 1 cup of sugar, cinnamon, and the melted butter, and set aside ¼ of the mixture to sprinkle over the top.
Butter a 9-inch spring form pan; spread and press zwieback mixture on bottom and side of form.
For the Filling: Beat eggs with sugar until light, add salt, lemon and vanilla. Stir in the cream, then add cheese and flour, mixing until smooth.
Strain through a fine sieve, or pour into food processor, or in batches in a food processor, and process until smooth.
5 Pour into zwieback-lined form, sprinkle remaining zwieback crumb on top, and bake for 1 hour.
6 Turn off heat, let stand in oven for 1 hour, or until cooled. Remove rim of spring form pan and place with tin bottom on serving plate.
