Grate the rind and strain the juice of two lemons. Pare, core and chop fine one large tart apple. Round two crackers very fine. Mix with two teaspoons melted butter. Mix the lemon juice and rind and apple with two scant cups of sugar. Beat the yolks of two eggs to a thick froth  and the whites stiff, mix and beat together and mix with the lemon, apple and sugar and add crumbs and butter. Beat thoroughly and line two pie tins as for custard pie. Pour in filling and bake until crust is done.