Start with the dough. In a bowl, add the flour, salt, vinegar, and sunflower oil. Gradually add the warm water (as needed) and knead until you have a soft dough that pulls away from the sides of the bowl. Knead well for 5 minutes. Once ready, cover the dough with plastic wrap and let it rest while you prepare the filling.

Add olive oil to a skillet. Sauté the yellow onion over high heat until softened. Lower the heat and add the green onion, leek, and spinach. Season with salt and pepper and sauté for 5 minutes. Add the dill.

Let the filling cool for 15 minutes. Crumble the feta cheese by hand and add it to the mixture. Beat the egg and add it as well. Mix everything well.

Brush the baking pan with oil and add the first sheet of dough. Spread the filling evenly in the pan.

Roll out the second piece of dough and place it on top. Fold any excess dough over the edges to seal the pie. Score into pieces and brush the top with oil.

Bake at 400°F (200°C) for about 45 minutes. Start with the lower oven rack for about 20 minutes, then continue baking with convection (fan) for the remaining time.