Place the salmon fillets on a microwave-safe plate, cover loosely with plastic wrap, and microwave for 2-3 minutes. Remove the skin and bones, then flake the salmon. Separate the shimeji mushrooms into small clusters, cut the king oyster and shiitake mushrooms into bite-sized pieces, and thinly slice the onion. Grate the lemon zest.

Heat 1 tbsp of olive oil in a frying pan and sauté the mushrooms. Remove them from the pan, add another 1 tbsp of olive oil, and sauté the onion until softened. Add the flaked salmon and return the mushrooms to the pan.