Cook the potatoes in boiling salted water for 6-8 mins until tender, then drain. Beat together the cream, eggs, dill, lime zest, salt and pepper. Scatter half the potatoes over the bottom of the pastry case, then put half the salmon strips in the gaps. Pour over half the egg mix, then arrange the remaining potatoes over the salmon pieces and put the remaining salmon in the gaps between. Pour over the rest of the egg mix.