Melt the butter slowly over low heat until it's fully liquid.
You can use either a saucepan or microwave for this.
In a mixing bowl or double boiler, whisk together the egg yolks and water until the mixture becomes slightly thick.
Place the bowl over simmering water, ensuring the bottom does not touch the water.
Continue whisking while gradually adding lemon juice.
Slowly pour the melted butter into the egg mixture while whisking constantly.
This is essential for the emulsion process.
Season with salt and a dash of cayenne pepper to taste.
Remove from heat once thickened.
Serve immediately.