Rinse the matie fillets briefly under cold running water, dab dry and dice finely. Peel and chop the onions. Bring to the boil briefly in 2 tablespoons of lemon juice and fold into the matie swell.
Cover and allow to draw a little. Wash the apple, cut out the core and cut the apple into 8 slices. Sprinkle with remaining lemon juice. For the sauce, wash the dill, dab dry and chop finely, except for a few flags for garnishing.
Mix crème fraiche and chopped dill. Season to taste with salt, pepper and curry. Arrange the matie tartar with some sauce on the apple slices. Serve with 1 slice each of pumpernickel and lemon. Dust the sauce with curry and sprinkle the tartar with grated lemon.
Garnish with dill flags and, if desired, with some dill blossom.