Cook the pasta in boiling salted water until just al dente. Set aside 100 ml of cooking water, drain the pasta.
Heat the butter in the same pan. Briefly sauté the spring onions and poppy seeds. Add the single cream for sauces, lemon zest and juice, season, simmer for approx. 1 min. Add the pasta and reserved cooking water, mix and heat gently. Scatter over the reserved spring onion greens, serve with cheese.