Wet the rim of a margarita glass or tumbler by rubbing a lime wedge around its circumference. Rotate the rim of the glass in kosher salt spread on a flat plate. Fill the glass about halfway with ice cubes.
In a cocktail shaker filled with ice, combine guava nectar, tequila, triple sec, and freshly squeezed lime juice. Shake vigorously, then strain into the prepared glass. Garnish the rim with a lime slice or wedge, if desired. Serve immediately.
I could only find Goya guava nectar at my local grocery store, so that is what I use in these photos. With that said, it contains red #40 dye, which I usually try to avoid. If you can find them at your grocery store, or plan ahead enough to order them online, try Iberia guava nectar or Grown Right organic guava nectar. Neither contain artificial dyes.
Don't like salt rims on your guava margaritas? No problem! Rim your glasses with sugar or nothing at all. A colorful fruity flavored sugar such as this mango cocktail sugar would be delicious as well as color coordinated with the drink.