The most obvious variation of Beurre Blanc involves replacing the white wine with red wine and the white wine vinegar with red wine vinegar. The resulting sauce, however, has a pale purple cast that reminds some people of Pepto-Bismol. To deepen the color of the sauce, reduce a bottle of full-bodied red wine with no tannin and low acidity to ½ cup (125 milliliters). Replace the vinegar called for in a classic beurre blanc with red wine vinegar. Combine the vinegar, red wine reduction, and shallots in a saucepan. Reduce as needed and whisk in the butter.

Unfortunately, Beurre Rouge often has a one-dimensional flavor and may even have an unpleasant metallic taste, because the wine is reduced without any protein that would remove the astringent tannins and deepen the flavor. A better approach is to make a red wine brown sauce containing reduced stock or demi-glace.