Shake tequila, sherry, and lime juice in a cocktail shaker with ice for about 30 seconds. Strain into a rocks glass with fresh ice. Gently pour 1/2 ounce red wine (fruity wine works best - try Malbec or Shiraz) of the back of a spoon held just above the drink's surface, so the wine lightly floats on top. Garnish with a lime wedge. This recipe is courtesy of Tacoteca in Santa Monica.