Preheat the oven to 400. Lightly brush a baking sheet with olive oil.
Place the almonds in the bowl of a food processor and pulse until coarsely chopped. Transfer to a plate.
Season the halibut with the salt and pepper; brush the flesh side of each fillet with 1 t. of the mustard. Dip the mustard side of each fillet into the almonds, pressing firmly to help the nuts adhere. Place the fillets, nut-crusted side facing up, on the prepared baking sheet.
Bake the halibut until the fish flakes easily with a fork and the nuts are browned, about 10 minutes. Remove from the oven.
Combine the parsley, lemon juice, lemon zest, and olive oil in a small bowl. Spoon over the fish and serve immediately.