Fish Rolls with Spinach Filling and Tomato Sauce

For the dough, melt margarine. In a mixing bowl, mix flour, egg, water and margarine. Knead with dough hook of hand mixer until dough is smooth. Cover and let stand for 30 minutes.

For the spinach filling, rinse spinach thoroughly and do not spin dry. Cook wet spinach in a pan. Peel onion and finely chop. Heat oil in a large pot and sauté onion until translucent. Drain spinach in a colander. Then squeeze out excess water and pat with paper towel. Add spinach to pan and mix with onion. Season with salt and pepper. Pat fish pieces dry and cut into small pieces and poach in salted water for 2 minutes. Lift fish pieces from water with a slotted spoon and drain in a sieve. Drain crab meat and cut into pieces.

Roll out dough on a floured tea towel in a thin layer. With floured hands, reach under dough and stretch dough until dough is very thin. Place spinach filling, fish pieces and crab meat evenly over  dough. Fold edges of dough over filling about 5 cm (approximately 2 inches). Use tea towel to roll up dough into a cylinder. Place on a baking sheet lined with parchment paper with seam side down. Whisk egg yolk with milk in a small bowl. Brush dough with egg mixture. Bake in preheated oven at 180°C (fan: 160°C, gas mark 2-3) (approximately 350°F), about 30 minutes.

For the tomato sauce, cut a shallow "X" on the bottom of each tomato with a sharp knife. Blanch tomatoes for 1 minute in boiling water. Drain and rinse in cold water, then drain again. Peel tomatoes and cut into quarters, remove seeds and cut into small cubes. Peel onion and finely chop. Heat butter in a pan and sauté onion until tender. Stir in tomato paste and cook briefly, then stir in diced tomatoes. Bring to a boil and continue to cook until sauce is reduced in volume and creamy. Season with salt, pepper and sugar.