3. Combine wet ingredients: mayonnaise, dijon and lemon juice.
4. Spread olive oil and bottom of baking pan, place barramundi filets in pan and add salt and pepper. Spread mayonnaise mixture on top of the fish this will act as the glue to hold the pistachios. Then add the pistachio mix on top of the fish.
5. Place in oven and bake for 12 to 15 minutes until fish flakes apart.