Firm white fish simmered in coconut milk with red curry paste, tamarind and Thai basil.
This one's already gluten free as written. Just check the label on your red curry paste and fish sauce, some brands add wheat-based thickeners.
Spoon the sauce over the fish rather than stirring it through. Fish breaks up fast if you use a spatula like you would with prawns or chicken.
Any firm white fish fillet works the same way. Thinner fillets need less time, thicker ones need a bit more, so check at the 5-minute mark before assuming it's done.