Mix the soy sauce, sour cream, lemon zest and half of the spices in a bowl.
In a large pan, boil water with a big pinch of salt. Cook the spaghetti for 5 minutes. No longer, as it will continue to cook in the oven.
Drain the spaghetti and save 100 ml of the cooking liquid.
In a large pan, mix the spaghetti and the frozen peas with the cooking liquid and the sour cream mixture.
Divide the spaghetti over the four sheets of baking paper, place a piece of salmon on top of each serving of spaghetti and sprinkle with the rest of the spices.
Tightly fold each sheet of baking paper into a packet so no steam can escape. Place the packets on a rimmed baking tray and bake in the oven for 12 minutes. Serve immediately and open the packets at the table.