Cook the pasta in a large saucepan of boiling water according to the packet directions, until firm-tender. Add the peas to the water during the final 1 minute of cooking; drain.
Meanwhile, combine the dill, spring onions, oil, lemon zest and lemon juice in a large bowl. Add the hot pasta and the peas, tossing well. Add the smoked salmon and a good grinding of pepper, then toss again.