Make a dough from the first six ingredients and roll out into a rectangle.
Briefly sauté the spinach with onion in a little oil and leave to cool. Mix in two eggs and feta. Spread this filling on 3/4 of the rolled out dough and shape into a roll.
Cut 2cm deep slits with a knife (crosswise) and bake in a preheated oven (180 degrees) for 30 to 35 minutes.