Whisk GF flour and salt in a large cold bowl.
Cut in cold butter with pastry cutter until mixture resembles coarse crumbs with pea-size butter pieces.
Stir in lemon juice. Add ice water 1 tbsp at a time until dough just clumps together.
Shape into flat disc, wrap tightly, refrigerate 1 hour minimum.
Roll into 8x12-inch rectangle between parchment sheets. Fold into thirds. Rotate 90°. Repeat 3–4 times.
Wrap and refrigerate another 1 hour.
Roll to desired thickness. Cut, fill, seal, egg wash. Bake at 400°F (200°C) for 18–22 minutes until deeply golden. Check at 16 minutes.
Use parchment to avoid over-flouring the dough.
Keep everything cold to ensure flaky layers.
Dough can be frozen for up to 1 month.