To make this margarita, start by preparing the jalapeño simple syrup. Heat a small saucepan, on the stove, over medium heat,
Next, slice the jalapeños and add them to the pot alongside the monk fruit sweetener and water. Stir to combine.
Bring the mixture to a gentle boil and allow it to cook until the sugar has cooked down / dissolved.
Once the sugar has dissolved, remove the syrup from the heat and allow it to cool.
Then, muddle the jalapeños into the syrup.
Transfer the syrup to a jar and allow it to continue to cool while you prepare the rest of the margarita.
Cut the watermelon into chunks and add them to a blender. Blend until the watermelon is totally smooth.
Strain any remaining chunks from the watermelon and transfer the liquid to a pitcher alongside the tequila, cointreau, lime juice, and the jalapeño simple syrup.
Stir the margarita together, then transfer it into glasses. You can rim the glasses beforehand with tajin, if desired. Just rub some of the simple syrup across the glass and dip it into the tajin!
Garnish with slices of jalapeño and watermelon, if desired. Then, serve and enjoy!