In a sauce pan or frypan large enough to hold the pasta when it is done combine the butter, cream and beef stock then simmer over medium heat until reduced by about half. Add the lemon juice, lemon and lime zest and set aside.
Bring a large pot of lightly salted water to a boil. Add pasta and cook for 8 to 10 minutes or until al dente; drain. Toss pasta with sauce; serve.