Fill a cocktail shaker with ice.
Add the mezcal, lime juice, triple sec, melon liquor, limoncello and simple syrup.
Cover and shake until mixed and chilled, about 30 seconds.
Place Lime-Tajin on a plate.
Press the rim of a chilled rocks glass into the mixture to rim the edge.
Add ice cubes, strain margarita into the glass.
Enjoy!