prepare the dough
Sift the flour into a large bowl. Use your fingertips to rub the butter into the flour until there are no large lumps of butter remaining. Bring water to a boil and add it to the flour mixture. Knead into a nice, elastic dough. Wrap in plastic wrap and place in the fridge for about 30 minutes.
marinate the salmon
Meanwhile, marinate the salmon. Pat dry your salmon fillet, remove the skin.
Add salt, sugar, lemon zest, dill and soy sauce to a baking dish. Stir to combine and place the salmon on top. Roll the salmon in the mixture and place the baking dish in the fridge for 20 minutes for the salmon to marinate.TipMake sure not to leave the salmon marinating for more than 20 - 30 minutes. If you leave it for longer, the salmon will be too salty and it will lose too much liquid which will result in a not perfectly juicy salmon dish.
Roll out the dough
Preheat your oven to 210 °C / 410 °F. Lightly dust the working surface and roll the dough into a rectangle approx. 30 cm x 20 cm (12-inch x 8-inch) and 2 mm / 5/64 inch thickness.
Remove the salmon from the fridge and rinse the marinate under cold running water. Pat the salmon dry using paper kitchen towels and place it in the center of your rolled dough. Fold the pastry over the salmon, cut off the unnecessary dough and then seal the edges by pressing them together with a fork. Make sure the salmon is carefully wrapped and sealed from all sides, just like in the photo.TipAt this point, you can freeze the salmon Wellington or leave it in the fridge for up to 6 hours.
Transfer the salmon wellington to a baking sheet lined with parchment paper and brush using an egg wash. Using a teaspoon make semicircles in the dough to create a fish scales pattern. Be careful not to press to hard or there might be holes in the dough.
Place the baking sheet with salmon wellington to the oven and bake for 20 minutes on the middle rack, then after 10 minutes of baking, rotate the baking dish for 180 degrees and bake for another 10 minutes. You might need to bake it longer than 20 minutes in total if your salmon fillet is thick. After 20 minutes of baking, increase the heat to 230°C / 450 °F. Then transfer the baking dish to a higher rack and bake for another 4 - 5 minutes or until the crust is beautiful, golden brown.
Remove the baked Salmon Wellington from the oven and transfer it to a wire rack for about 5 minutes, then cut using a serrated knife into five slices. Serve with a side of your choosing. Make sure each slice is at least 3 cm / 1.2 inch thick or it may fall apart.