In a small bowl, combine the butter, nuts, parsley and lemon juice.
Prepare a hot fire in your grill or bring your indoor grill to medium high.
Rinse the fish and pat dry with paper towels. Brush the fish with olive oil and season to taste with salt and pepper.
Place the fish flesh side down on the grill. Grill for 10 minutes per inch of thickness, turning once, until the fish is firm.
Serve each fillet with a dollop of Macadamia butter.
If not serving the Macadamia butter immediately, spoon it into a ramekin and cover with plastic wrap. Store in the refrigerator for up to a week or wrap in additional freezer plastic and freeze for up to 3 months.