Preheat oven to 375°F and line a large baking sheet with parchment paper.
Clean and slice the leeks into thin ribbons, soaking them in cold water to remove grit before patting them completely dry.
Trim the woody ends from the asparagus and toss both the asparagus and leeks with olive oil, sea salt, and black pepper on the baking sheet.
Roast the vegetables for 15 minutes to begin the caramelization process.
While vegetables roast, prepare the crust by finely mincing the macadamia nuts and mixing them with lemon zest, garlic powder, and fresh parsley.
Pat the salmon fillet dry with a paper towel and coat the top surface with a thin, even layer of Dijon mustard.
Press the macadamia-herb mixture firmly onto the mustard-coated salmon to create a thick crust.
Move the par-roasted vegetables to the sides of the pan and place the salmon fillet in the center.
Return the pan to the oven for another 12-15 minutes until the crust is golden and the salmon flakes easily with a fork.
Drizzle the fresh lemon juice over the salmon and vegetables just before serving to brighten the savory flavors.