01 - Preheat oven to 425°F. Line a rimmed baking sheet with parchment paper for easy cleanup.
02 - Arrange trimmed asparagus spears in a single layer on prepared baking sheet. Drizzle with olive oil, then sprinkle evenly with kosher salt and black pepper. Toss gently to coat all spears.
03 - Roast for 12-15 minutes until tender-crisp and lightly browned, shaking the pan halfway through for even cooking. Cooking time may vary based on spear thickness.
04 - While asparagus roasts, whisk egg yolks and lemon juice in a heatproof bowl until thickened and doubled in volume, about 1-2 minutes.
05 - Set the heatproof bowl over a saucepan with 1 inch of barely simmering water, ensuring the bowl does not touch the water. This gentle heat prevents the eggs from scrambling.
06 - While whisking constantly, slowly drizzle warm melted butter into the egg mixture in a thin stream. Continue whisking until sauce thickens and becomes creamy, about 3-4 minutes.
07 - Remove from heat immediately. Whisk in sea salt and cayenne pepper to taste. Keep warm over the warm water bath (not on direct heat) if not serving immediately.
08 - Transfer roasted asparagus to a serving platter. Spoon warm Hollandaise sauce generously over the spears or serve alongside in a small bowl. Serve immediately while sauce is warm and asparagus is hot.