Beat butter, sugar and salt until blended; beat in egg yolks and vanilla. Beat in sour cream. Gradually beat in flour. Divide dough in half. Shape each into a rectangle; wrap in plastic. Refrigerate until firm, about 1 hour., Preheat oven to 375°. On waxed paper, roll one half of dough into a 14x10-in. rectangle. Transfer to a greased 13x9-in. pan; press onto bottom and 1/2 in. up sides of pan. (Dough may crack; pinch together to patch.) , For filling, mix sugar, flour and cinnamon; toss with apples. Place in crust; dot with butter. On waxed paper, roll remaining dough into a 14x10-in. rectangle; place over filling. Pinch edges to seal., Whisk egg white until frothy; brush over top. Sprinkle with pecans. Cut slits in top crust. Bake on a lower oven rack until golden brown, 40-45 minutes. Cool on a wire rack.