In a ramekin or blender add egg yolks, lemon juice, salt, and cayenne pepper. Pulse blender once to just break up the egg yolks and slightly combine.
Melt the butter. The butter needs to be HOT, this is what cooks and emulsifies the egg yolks. Melt butter in a microwave or on the stove just until the butter starts to bubble, make sure the butter doesn’t burn or brown! The butter will need to be put into a container with a good pouring spout. You need to have absolute control over the pouring speed of the butter.
Immediately after the butter is melted, and hot, turn on the blender on a low speed. Slowly trickle the hot butter into the egg yolk mixture. Once all of the butter is added continue blending for 20-30 seconds. Turn the blender off, the hollandaise sauce should be silky smooth and thick.
If the sauce has separated, that means the butter was added too quickly and the oil has not combined with the yolks. If this happens discard sauce and start over.