Season the fish with salt, season with pepper and rub with the juice of the lime. Clean the celery and cut into 1 cm pieces. Clean bell bell pepper and cut into cubes.
Rinse grapefruit and fillet. Remove fruit fillets precisely from dividers and set aside, reserving juice.
Squeeze out remaining grapefruit. Blanch celery and peppers in boiling hot salted water for 5 min, then place in iced water.
Sauté fish heartily in butter, remove and keep warm. Add oil and juice of grapefruit to frying pan and cook, add celery and peppers and season repeatedly. Then add the fruit fillets and heat briefly and arrange the whole thing on the plate. Long grain rice is very suitable as an additional dish.
Tip: Use creamy natural yogurt for an even finer result!