Method

• Make the pastry: In a large bowl, combine the flour and salt. Cut in the butter until the mixture resembles coarse crumbs. Gradually add the water, mixing until the dough just comes together. Form the dough into a disc, wrap in plastic wrap, and refrigerate for at least 30 minutes.
  
  
• Make the filling: In a large bowl, combine the spinach, feta cheese, onions, egg, dill, salt, and pepper.
  
  
• Roll out the pastry: Roll out the pastry on a lightly floured surface to a 12-inch circle.
  
  
• Add the filling: Spread the spinach mixture evenly over the pastry.
  
  
• Bake: Bake in a preheated oven at 375°F (190°C) for 30-35 minutes, or until golden brown and flaky.