Fill a shaker half-full with ice. Add tequila, lime juice, and sweetener to the shaker. Seal and shake vigorously until outside is frosted, 10 to 15 seconds.
Place salt on a plate. Run 1 lime wedge along the rim of the Mason jar. Press the jar down into the salt. Fill the jar with ice cubes.
Strain margarita into the jar. Top with sparkling water and stir. Garnish with remaining lime wedge.
If you have granular sweetener on hand instead of powdered, you can pulse it in a blender or food processor to achieve a powdered consistency.
Source: Read Full Article