From America's Test Kitchen Season 2: Fajitas and Margaritas
The typical margarita tends to be a slushy, headache-inducing concoction made with little more than ice, tequila, and artificially flavored corn syrup. We wanted a margarita with a balanced blend of fresh citrus flavors and tequila.
We found that the key was using the right proportions of alcohol and citrus juice—equal parts of each one. For a mellow, delicate flavor, we preferred reposado tequila, made from 100 percent blue agave, which is aged about 12 months. Unaged tequilas gave our margaritas a raw, harsh flavor. And those made with superpremium tequilas, which are aged up to 6 years, tasted smooth, but their distinct tannic taste dominated the cocktail. As for orange-flavored liqueurs, a lower-alcohol liqueur, such as triple sec, worked best. Mixes and bottled citrus juice had no place in our cocktail—instead we steeped lemon and lime zest in their own juice for a deep, refreshing citrus flavor. And with a bit of easy-to-dissolve superfine sugar and crushed ice, our margaritas were complete.
Makes about 1 quart, serving 4 to 6
The longer the zest and juice mixture is allowed to steep, the more developed the citrus flavors in the finished margaritas. We recommend steeping for the full 24 hours, although the margaritas will still be great if the mixture is steeped only for the minimum 4 hours. If you're in a rush and need to serve margaritas immediately, omit the zest and skip the steeping process altogether.