- To make the sauce, place the egg yolks and 2 tablespoons of the orange juice in a heatproof bowl or the top pan of a double boiler. Set the bowl or pan over but not touching hot or barely simmering water in a saucepan or the bottom pan of the double boiler. Whisk continuously until warm and just beginning to thicken, about 1 minute. Add the butter 1 slice at a time, whisking until fully absorbed before adding more. When all of the butter is absorbed, continue to whisk until thickened, 2 to 3 minutes. Do not overcook.
- Remove the bowl or pan from the pan of hot water, and season the sauce with salt and pepper. If the sauce is too thick, stir in as much of the remaining 1 tablespoon orange juice as needed to thin to the desired consistency. You should have about 3/4 cup sauce. Remove the bottom pan from the heat and let the water cool slightly. Then set the bowl or pan with the sauce over the warm water and cover loosely with a paper towel to prevent a skin from forming.
- Cut or break off the tough white ends from the asparagus spears. Trim all the spears to the same length. If the spears are large, use a vegetable peeler to peel away the tough skin, starting 2 inches below the tip.
- Pour water into an asparagus steamer, add the 2 teaspoons salt and bring to a boil over high heat. Place the spears, tips up, in the basket and steam just until tender, 2 to 3 minutes.
- Remove the asparagus from the steamer and divide among 4 warmed plates, arranging the spears in a row. Spoon the warm Hollandaise sauce in a wide stripe across the middle of the asparagus. Using a zester or fine-holed shredder, and holding the orange over each serving, shred a little zest from the orange peel directly over the Hollandaise on each serving. Serve immediately.