If using, rim a margarita glass with chili powder and salt. To do this, rub a lime wedge around the rim of the glass and dip the rim in a mixture of chili powder and salt.
In a cocktail shaker, combine tequila, guava puree, lime juice, triple sec, and agave syrup (if using).
Fill the shaker with ice.
Shake well until the outside of the shaker is frosty (about 15-20 seconds).
Strain into the prepared margarita glass filled with ice.
Garnish with a lime wheel or a slice of guava, if desired.
Notes
Enjoy responsibly! Feel free to adjust the sweetness to your liking by adding more or less agave syrup.