Spread out a sheet of aluminium foil. Put the salmon piece in the middle and season with salt and pepper. (The foil should be long enough to wrap the contents and fold over, about 26 cm.)
Top with sliced onion and mushrooms of your choice, sprinkle with lemon juice and top with the butter.
Bring the edges of the foil over and fold over three times with about a 1.5 cm seam.
Fold up the sides too to seal the packet.
Bake in a toaster oven for about 18 minutes and it's done.
(Our toaster oven is a 1200 W model with heating elements on both the top and bottom.)
Story Behind this Recipe
My mother taught me this recipe. I increased the vegetables for my children. I used plenty of Hiroshima lemon, but feel free to use what's available where you live. This is the very first foil bake I've ever made, and I've been making it for a long time since it's so delicious.
Use raw salmon, not salted salmon. If you don't like lemon (like my husband) just leave it out. The salmon is steam-cooked in the moisture that comes out of the onion and mushrooms. Toaster ovens vary, so please use the cooking times as a guide. If you're making this in an oven, baked for about 18 minutes at 250°C without preheating.