In a large saucepan of boiling salted water blanch the snap peas for 1 minute, drain them, and plunge them into a bowl of ice and cold water to stop the cooking. Drain the peas well. The peas may be prepared up to this point 1 day in advanced and kept covered and chilled. In a large heavy skillet melt the butter with the zest, add the peas and salt and pepper to taste, and heat the peas over moderately low heat, stirring, until they are hot.
