Place kosher salt on a small plate. Run a slice of lime all the way around the rim of a lowball glass, then dip rim in kosher salt. Fill glass with ice and set aside.
Add all ingredients except for salt to a cocktail shaker filled with ice. Shake vigourously to fully combine and chill. Strain margarita into prepared glass. Garnish with a slice of lime if desired.
Notes
To make simple syrup, combine equal parts granulated sugar and water in a sauce pan over low heat, stir until sugar has dissolved. Allow to cool and store in a sealed container in the refrigerator.