In a saucepan, melt butter and skim off foam. Combine egg yolks and wine in a metal bowl and place over a pan of hot water. Beat until creamy. Remove bowl from heat. Add melted butter, drop by drop to begin with, until incorporated. Then add butter in a thin stream, whisking constantly, until sauce is creamy and glossy. Season with lemon juice, salt and pepper.
Serve sauce garnished with lemon and lime zest.