If making the filling, cook the spinach and set aside. Finely chop onions and saute in olive oil. Add salt and pepper. Set cooked items aside.
Dissolve yeast in water. Mix flour and salt in bowl. Add yeast and water and yogurt to bowl. Mix together until elastic. Add more flour if mixture is too sticky. Let dough rise. Portion dough into 80-100 g pieces. Roll out a few balls at a time (i.e 4 or 5) into flat circles, preferably as thin as possible - this is especially important if adding a filling to Gözleme. Dust each piece of dough well with flour to prevent sticking. Cover dough pieces as you work, allowing dough to breathe and rise lightly. Do not roll out too many pieces ahead of time to prevent the dough from rising too much and the bread sticking together. Lightly coat bread with oil*.
Cook bread on metal skillet on medium high heat. Check frequently for puffing up of dough and flip when dark brown spots start to appear. These are the “Goz” (Turkish word for eyes), from which the bread’s name, Gözleme comes from. Flip and cook on other side. Repeat. Each side will only require cooking for 1-2 minutes if cooking without the filling.
*Optionally, add filling to Gözleme. Begin with cooked spinach, then mix together onions and parsley. Lastly, add a thin layer of feta cheese. Fold the raw dough in half, pinch sides to seal shut, and then begin cooking on one side. Once browned flip over and cook the other side.