Cut carrot, onion, lemon and mushroom thinly.
Prepare a 10” x 10” (25 x 25 cm) aluminum foil sheet. Add olive oil where salmon goes to avoid sticking salmon and aluminum foil.
Add the onion first, then salmon on top. Add butter, mushrooms, and carrots on top of the salmon.
Before adding other ingredients, let's close the sides of the foil tightly. After closing sides, top is open.
From top, add sake, soy sauce, black pepper, and lemon. Close the top of the foil tightly.