Heat a dry non-stick pan and put the cucumber quarters seed side down in the pan. Leave them that way until seared and toasted. Add a knob of the butter and a pinch of salt to the pan and turn the cucumber over. Continue to cook for a few more minutes. Remove and set aside.
Heat a saucepan and add the shallots, wine and vinegar and cook until the shallots are soft. Transfer to a blender or food processor and blend until smooth. Pass through a sieve.
Add a tablespoon of the shallot purée and the cream to a separate pan. Heat the shallot cream, then add the diced butter a bit at a time.
Once fully incorporated, season with salt, cayenne pepper and lemon juice.
Heat a medium frying pan and add the oil. Once hot, add the fillets and cook for two minutes on each side. (Add a knob of butter and a squeeze of lemon juice towards the end if you want to add more flavour. Spoon the melted butter over the fish.)
To serve, place the seared cucumber on each plate, then lay the fish next to the cucumber.
Dress with the sauce and cress and flowers.