1. Remove any prominent bones from the fish fillets using tweezers. Season the flour with salt and pepper on a large plate and press the fillet into the mix to coat on either side. Shake off any excess and set aside on a clean plate.
2. Heat the oil in a frying pan, which is big enough to accommodate the fish fillet over a high heat. Add the fish fillet, skin-side down and asparagus and cook for 2 minutes and then turn over the fish add half the butter and a squeeze of lemon and cook for a further minute until golden and butter melts. Using a fish slice, remove the fillets from the pan and set aside on a warmed plate
3. Place the pan back over a high heat and melt the butter until it is foaming, then add the lemon juice and continue to cook until the butter turns a nutty golden brown
4. Pour the butter, lemon mix over the fish. Warm the lentil in the pan with the remaining pan sauce and serve straight away.