Melt the butter and fry (sauté) the onion until soft
but not brown.
Add the chicken and fry for 3-5
minutes until cooked and lightly golden. Add the
lemon rind and juice and cook, scraping up any meat
residue until almost evaporated.
Stir in the cream
and simmer until thickened and reduced by half. Stir
in the capers, half the parsley and a little salt
and pepper.
Meanwhile, cook the pasta according to
the packet directions. Drain and pile on to warm
plates.
Spoon the chicken sauce over and garnish
with the remaining parsley.