Method 1: Double boiler

Cup of Yum
1. Fill a pot with about 2 inches of water and bring the water to a simmer. Place a metal bowl over the pot, big enough that it doesn't touch the water.
2. Add the egg yolks and lemon juice to the bowl. Whisk vigorously for about 3 minutes, until the yolks lighten in color and thicken. Remove the bowl from the pot and set it aside.
3. Heat the butter in a saucepan, over medium heat, just until it melts, then remove it from the heat. While whisking vigorously, very slowly pour the butter into the egg yolks. Mix until the sauce is thick and velvety.
4. Whisk in the salt and cayenne pepper. Serve warm.

Method 2: Blender

1. Melt the butter over medium heat until bubbly and frothy.
2. Add the yolks and lemon juice to a blender. Blend on high speed for a few seconds, then remove the funnel from the middle of your blender lid.
3. While still blending on high speed, slowly pour the hot butter into the blender. Mix until thick and creamy. Add the salt and cayenne pepper, then pulse the blender a few times.
4. Scrape the sauce out of your blender and serve warm.