Preheat the broiler in your oven to high and set the oven rack about 6 inches below it.
Place the salmon on a baking sheet and brush it with the grapeseed oil. Season it with the salt, pepper and garlic powder.
Broil the salmon for 6 to 8 minutes, or until just opaque and flakes easily with a fork. If you’re doing a large filet, broil it for 8 to 10 minutes, then check. The time will depend on the thickness of the filet!
To assemble the salad, toss together the lettuce with a pinch of salt and pepper, the orange segments, grapefruit, avocado and shallot. Drizzle with the vinaigrette. Sprinkle with the feta before serving.