In a heatproof bowl, whisk together the egg yolks and lemon juice until pale and thick.
Place the bowl over a saucepan of simmering water, ensuring the bowl doesn't touch the water.
Continue whisking until the mixture doubles in volume and becomes creamy.
Slowly drizzle in the melted butter while whisking continuously.
Keep whisking until the sauce thickens and is smooth.
Season with salt, white pepper, and a pinch of cayenne, if desired.
Remove from heat and serve immediately or keep warm.
If the sauce is too thick, whisk in a few drops of warm water to reach desired consistency.
Use immediately or store in a warm place until ready to serve.
Be cautious not to overheat, as it can cause the sauce to separate.