Sift flour and salt together into a medium bowl. Cut in butter as for pie crust to pea sized pieces. Set aside.
Put warm water and 1 teaspoon sugar in a large bowl. Add yeast. Let dissolve. Add slightly beaten egg yolks to yeast mixture.
Add flour mixture and gently mix until mixture forms a ball. Divide in half. Use one-half for bottom and one-half for top crust. Roll out one crust to fit a 9×13 inch ungreased pan. Sprinkle tapioca over dough.
Fill with sliced apples, piled high. Sprinkle with mixture of 3/4 cup sugar and 1 teaspoon cinnamon.
Roll top crust to fit pan. Put top over apples, seal in around pan, tucking top under (do not flute). Do not prick.
Bake at 350 degrees F (175 degrees C) for 45 minutes. While still slightly warm, frost with butter frosting.