Place the flour in a bowl, make a well in the centre and add the salt, olive oil and vinegar.  Knead to mix, while adding enough warm water to achieve a smooth, soft dough, that is does not stick to your hands.

In a pan, sauté the onions, the  leeks, the dill and the spinach in olive oil. Add the pepper.

Remove the pan from the stove and let the filling cool down.

Grease a medium-sized ovenproof dish well.

Roll out  3/4 of the dough, thin, and wide enough to cover the bottom and the sides of your dish. Arrange it in the dish, and brush lightly with olive oil.

Add half of the filling and sprinkle with half of the feta cheese.

Take a small portion of the remaining dough and roll it out to cover the surface of the filling.

Repeat with the rest of the spinach filling and feta cheese.

Roll out the rest of the dough, and cover the pie.

Brush with olive oil and melted butter, score into pieces, and bake in a preheated oven, at 180 degrees, for one hour.