Melt butter in a saucepan over low heat; skim off and discard foam. Reduce vinegar and wine with shallots and peppercorns in a saucepan over medium heat until it measures 3 Tbsp. strained liquid, 15-20 minutes. Simmer 1-inch water in a saucepan over medium-low heat. Whisk egg yolks and vinegar reduction in a stainless steel bowl. Place bowl over simmering water (don't let bowl touch water). Whisk mixture vigorously until yolks begin to thicken and whisk begins to leave trails, 2 minutes. Remove bowl from heat. Off heat, whisk in 2 tsp. lemon juice. Begin whisking butter into yolk mixture a drop at a time. As the mixture starts to thicken, whisk in remaining butter in a thin stream. If the mixture gets cold, return bowl to pan of simmering water and continue whisking in butter. Whisk in remaining lemon juice; season with salt and cayenne. If sauce seems too thick, thin with a little warm water. To keep sauce warm, transfer to a heatproof vessel; place in a pan of warm water set over low heat. Stir sauce often to keep smooth.