Knead the dough. Pour warm water into a deep bowl. Add sugar, vegetable oil and salt. Pour in the yeast. Stir. Gradually add flour, stirring constantly. Place the dough on a table sprinkled with flour. Knead for 5-6 minutes until it becomes elastic and smooth. Cover with a clean towel and leave in a warm place for 1.5 hours.
While the dough is resting, prepare the filling. Cut the onion into small cubes. Pour vegetable oil into the frying pan and put it on the fire. Put the onion in. Add salt, ground black pepper and stir. Fry until golden for 4 minutes. Turn off the heat and transfer the filling to a clean bowl.
Prepare the roll. Place the dough on a table sprinkled with flour. Roll out the layer to a thickness of 0.5 cm with a rolling pin. Place the onion filling on the dough. Roll the dough tightly into a roll. Bake the roll in the oven for 30 minutes at 180 ˚C.