Melt the unsalted butter in a saucepan over low heat.
In a heatproof bowl, whisk together the egg yolks and lemon juice until thick and pale.
Place the bowl over a saucepan of simmering water, ensuring it doesn't touch the water.
Continue whisking the egg mixture while slowly drizzling in the melted butter.
Keep whisking until the sauce thickens and doubles in volume.
Add salt and cayenne pepper to taste, mixing well.
If the sauce is too thick, whisk in a teaspoon of warm water to loosen it.
Remove from heat and serve immediately or keep warm.
Enjoy your hollandaise sauce drizzled over your favorite dishes!