Heat oven to 200C/fan 180C/gas 6. Mix the red pesto, lemon zest and olives together, then stir in the breadcrumbs.
Lay the fish fillets on a baking tray, skinside down, then press the crumbs over the surface of each piece. Bake in the oven for 10-12 mins until the fish is cooked through and the crust is crisp and brown.