Preheat your oven to 425º.
Line a sheet pan with parchment paper. Place salmon in middle of the pan and surround it with the mushrooms. Coat fish and mushrooms generously with cooking spray and sprinkle everything with ½ teaspoon salt and pepper. Roast until the fish flakes easily and is opaque in the center (test by poking it with a paring knife), and mushrooms are tender and browned in spots, about 25 minutes.
3. Meanwhile, place ½ teaspoon salt in a small bowl with shallots, sugar and red wine vinegar.
Stir well to dissolve salt and sugar and let mixture sit while the fish roasts.
Place olive oil, soy sauce, lemon juice and tahini in a large bowl and whisk until smooth. Season the dressing to taste with salt. Add arugula to the bowl and toss well to combine. Transfer arugula to a large serving platter.
Break fish into large pieces and place them on top of the arugula. Top fish with the roasted mushrooms and top those with the shallots and their pickling liquid. Top with the avocado and almonds. Serve immediately.