Wash asparagus and trim off bottom of stems by about 2 inches. In a large skillet, bring about 1/2 inch of water to a rapid boil. Season the water with salt and add the asparagus. Cook the asparagus for 2-3 minutes or until bright green and just tender. Drain the asparagus and add butter to the skillet. Stir in the zest and juice. Return the drained asparagus to the skillet and toss to coat. Serve immediately
Variation: After the asparagus is drained, refresh immediately in a bowl of ice water. This will help the asparagus to retain the bright green color. Serve the asparagus cold with vinaigrette.