Add 300 ml of lukewarm water, 1 teaspoon of sugar, and 2 tablespoons of flour to the yeast. Mix and let it rise in a warm place for 10-12 minutes.
Meanwhile, prepare the filling by slicing the onion into half-moons and frying it in oil. Add paprika and black pepper, then let it cool.
Make a well in the flour, add salt, and mix in the risen yeast to form a soft dough. Let it rise again in a warm place for about 20 minutes.
Roll out three dough sheets. Grease a 30 cm diameter baking tray with oil and a little flour. Place the first sheet, which should be larger than the tray.
Spread the cooled onion mixture on top, add the second sheet (equal to the tray diameter), layer more filling, then place the third sheet and fold the edges of the first sheet over.
Brush with egg yolk and bake at 190°C (no fan) for about 35-40 minutes. Optionally, serve with fried bacon.