Everyone's doing beurre blanc, so let's give it a try.
Reduce 100ml each of white wine and vinegar in a pot with a sprig of tarragon, a bay leaf, ten black peppercorns and a chopped shallot. Cool and strain. Place two tablespoons of this reduction into a pot with a tablespoon of cream. Reduce this by half and then gradually whisk in 200g cold diced, butter until thickened slightly. Add the juice of half a lemon, salt and pepper. Fold in a slew of capers, maybe a dozen.
Meanwhile, cut four peeled waxy potatoes (those red ones that seem to change their names every week or so - Pontiac? Red Devil? Red Russet? - will be fine) into half-centimetre slices, boil until yielding but not quite mashable. Drain.
Meanwhile, cook salmon fillets gently in a pan with a little lemon juice, lime juice or orange juice; or a little of all three.
Layer potatoes on serving plates, salmon on top, beurre blanc over.