Pat fish fillets dry with paper towel and dust with seasoned flour, shaking off any excess.
Melt half of butter in a large frying pan on medium heat. When starting to sizzle, add fish fillets and cook for 2 minutes each side, until tender and golden. Remove to warm plates.
Add remaining butter and lemon juice to pan, increase heat to high and stir for 1 minute, until well combined. Stir through parsley. Serve fish with steamed potatoes and green beans and spoon over sauce.
