Prepare the dough: In a large bowl, whisk together flour, salt, sugar, and yeast. Gradually add warm water and 1 tablespoon olive oil, mixing until a shaggy dough forms.

Knead the dough: Turn the dough onto a lightly floured surface and knead for 5-7 minutes until smooth and elastic. Place in an oiled bowl, cover, and let rise in a warm place for 45-60 minutes, or until doubled in size.

Prepare the filling: While the dough rises, combine chopped spinach, crumbled feta, fresh parsley, black pepper, and the optional finely chopped onion in a bowl. Mix well until evenly combined.

Divide and roll: Punch down the risen dough and divide it into 6-8 equal pieces. On a lightly floured surface, roll each piece into a very thin, oval or rectangular shape, approximately 8-10 inches long.

Fill the flatbreads: Place about 2-3 tablespoons of the spinach and feta filling on one half of each rolled dough piece, leaving a small border around the edges. Fold the other half of the dough over the filling to create a half-moon or rectangular shape.

Seal and crimp: Gently press the edges to seal the filling inside, then use a fork to crimp the edges firmly, ensuring a tight seal to prevent the filling from escaping during cooking.

Cook the Gözleme: Heat 1 tablespoon of olive oil in a large non-stick skillet or griddle over medium heat. Carefully place one or two gözleme in the pan, depending on its size.

Flip and cook: Cook for 3-5 minutes per side, until each side is golden brown and crispy, and the filling is heated through. Add more oil as needed between batches to maintain even cooking and crispiness.

Serve: Remove the cooked gözleme from the pan and serve immediately while hot. Repeat with the remaining dough and filling until all gözleme are cooked.