Squeeze the lemon and mix the juice with the quark, yogurt and sugar in a bowl.
Peel, quarter and thinly slice the oranges. Put the cream in a measuring beaker and whip until stiff, then stir loosely into the quark cream with a fork.
Alternately fill four tall glasses with quark cream and orange slices, top with oranges and garnish the cream with flaked almonds if desired.