Cocktail:
Place tajin seasoning in a small shallow plate. Run a lime wedge around the rim of the glass and dip in the tajin seasoning. Set aside until ready to use.
Add frozen watermelon cubes, vodka, simple syrup (or sweetener of choice), jalapeño, lime juice, about 1 teaspoon of the remaining tajin seasoning and ice. Pulse until smooth.
Fill your glass halfway with ice and pour. Garnish with a lime slice and/or fresh mint. Enjoy!
Simple Syrup:
Combine all sugar and water in a small saucepan over high heat and bring to a boil, stirring until sugar is dissolved. Remove from heat and let stand at room temperature, covered, for 1 hour.