This frozen margarita was inspired by the flavors of a cool and creamy Key lime pie. Whip up a batch of these easy frozen margaritas for Cinco de Mayo or anytime you want a sweet and refreshingly tart treat! Use Key limes--which have a wonderful floral aroma and flavor--if you can find them, but common limes work as well. Freshly squeezed juice will have the best flavor, but you can also find bottled Key lime juice--just be sure to buy unsweetened juice if you go for packaged juice. If you prefer a mocktail, simply replace the tequila with water.