In a large mixing bowl, combine the all-purpose flour and salt. Mix well.
In a separate bowl, whisk together the lemon juice, vegetable oil, and cold water.
Gradually add the wet ingredients to the flour mixture, stirring until a dough begins to form.
Knead the dough on a lightly floured surface for about 5 minutes, until it is smooth and elastic.
Wrap the dough in plastic wrap and let it rest at room temperature for at least 30 minutes.
After resting, divide the dough into 4 equal pieces. Roll each piece out on a floured surface as thin as possible, ideally to about 1/16 inch thick.
Brush each sheet with melted butter before stacking them, if desired, for extra flakiness.
Use the rolled phyllo dough immediately or store it in the refrigerator for up to 2 days, or freeze for up to 2 months.