In large bowl, combine flour, ground pecans and salt.
Cut in shortening until mixture resembles coarse crumbs.
In small bowl, blend egg yolk, 4 tablespoons water and lemon juice.
Add to flour mixture, mixing lightly with fork just until dough sticks together.
Add more water, if necessary.
Press into ball.
Roll out on lightly floured surface into 10-inch circle.
Carefully fit into 9-inch pie plate.
Trim edge; flute as desired.
Prick bottom and side of pastry with fork.