What classic French sauce is made from egg yolks, butter, and lemon juice?

The classic French sauce made from egg yolks, butter, and lemon juice is hollandaise.

Hollandaise is an emulsion: egg yolks help bind melted butter and an acidic ingredient such as lemon juice, vinegar, or a white-wine reduction. Salt and white or cayenne pepper are common seasonings. Gentle heating is essential because excessive heat can cause the yolks to curdle and the sauce to split.

Despite its name, hollandaise is considered a French sauce. The name means “Dutch sauce” in French, but the sauce’s exact naming history is uncertain. A closely related recipe appeared in François La Varenne’s 1651 cookbook, and the sauce became firmly established in French culinary tradition.

Hollandaise is strongly associated with eggs Benedict and is also served with asparagus and other vegetables. It is related to béarnaise, another egg-yolk-and-butter emulsion; béarnaise typically uses a reduction flavored with vinegar, shallots, tarragon, and chervil instead of lemon juice.