To make the spicy simple syrup:

1. In a small saucepan, combine sugar and water. Bring to a simmer over medium heat, stirring until sugar is dissolved.
2. Add the sliced habanero to the pan and let it steep for about 10 minutes. For a spicier syrup, you can increase the steeping time.
3. Remove from heat and allow to cool.
4. Strain out the habanero slices and store the syrup in an airtight container in the refrigerator for up to two weeks.

To make the watermelon juice:

1. Cut the watermelon into large chunks, compost the rind.
2. In a blender, blend the watermelon chunks until smooth.
3. Over a bowl or pitcher, strain the blended watermelon through a fine mesh strainer to remove any seeds and pulp. Press gently with a spatula to extract as much juice as possible.
4. Store the juice in the refrigerator until ready to use.

To make the margarita:

1. Prep the Glass: Wet the rim of the glass with a lime wedge. Dip half the rim into kosher salt and set aside.
2. Mix the Drink: In a shaker, combine blanco tequila, Cointreau, habanero simple syrup, lime juice, and watermelon juice. Fill with ice and shake until combined.
3. Serve: Strain the mixture into the prepared glass filled with ice.
4. Garnish: Add a lime wedge to the side or atop the drink.
5. Enjoy!