Beurre noir is melted butter

Butter

Butter is a dairy product made by churning fresh or fermented cream or milk. It is generally used as a spread and a condiment, as well as in cooking applications, such as baking, sauce making, and pan frying...

 that is cooked over low heat until the milk solids turn a very dark brown. As soon as this happens, acid

Acid

An acid is a substance which reacts with a base. Commonly, acids can be identified as tasting sour, reacting with metals such as calcium, and bases like sodium carbonate. Aqueous acids have a pH of less than 7, where an acid of lower pH is typically stronger, and turn blue litmus paper red...

 is carefully added to the hot butter, usually lemon juice

Lemon juice

The lemon fruit, from a citrus plant, provides a useful liquid when squeezed. Lemon juice, either in natural strength or concentrated, is sold as a bottled product, usually with the addition of preservatives and a small amount of lemon oil.-Uses:...

 or a type of vinegar

Vinegar

Vinegar is a liquid substance consisting mainly of acetic acid and water, the acetic acid being produced through the fermentation of ethanol by acetic acid bacteria. Commercial vinegar is produced either by fast or slow fermentation processes. Slow methods generally are used with traditional...

. Some recipes also add a sprig of parsley

Parsley

Parsley is a species of Petroselinum in the family Apiaceae, native to the central Mediterranean region , naturalized elsewhere in Europe, and widely cultivated as an herb, a spice and a vegetable.- Description :Garden parsley is a bright green hairless biennial herbaceous plant in temperate...

, which is removed from the hot butter before the acid is added.

Beurre noir is typically served with eggs, fish, or certain types of vegetables.

See also

• Beurre blanc
  Beurre blanc
  Beurre blanc —literally translated from French as "white butter"— is a hot emulsified butter sauce made with a reduction of vinegar and/or white wine and grey shallots into which cold, whole butter is blended off the heat to prevent separation. The small amounts of lecithin and other emulsifiers...
  
  
• Beurre noisette
  Beurre noisette
  Beurre noisette is frequently used in French pastry production. It can also be used as a warm sauce to accompany many foods, such as winter vegetables, pasta, fish, omelettes, and chicken.Unsalted butter is melted over low heat and allowed to separate into butterfat and milk solids...
  
  
• French cuisine
  French cuisine
  French cuisine is a style of food preparation originating from France that has developed from centuries of social change. In the Middle Ages, Guillaume Tirel , a court chef, authored Le Viandier, one of the earliest recipe collections of Medieval France...