Brush the bottom and sides of the piecrust even with egg white. Bake on a baking sheet until light brown this will take about five minutes. Remove crust from oven. In a bowl, combine apples, lemon juice, sugars, flour, cinnamon, nutmeg, and salt. Mix well, spoon into crust.
Make the crumb topping by combining 3/4 cup flour, 1/4 cup sugar, 1/4 cup brown sugar in a bowl. Cut in 1/3 cup butter until crumbly. Sprinkle over the apple mixture.
Bake on baking sheet 50 minutes or until topping is golden and filling is bubbly.