Bring sugar, water, and lime juice to a boil over high heat in a medium saucepan. Lower heat to a simmer and let simmer for about 10 minutes, until sugar is completely dissolved and mixture has begun to thicken.
Transfer to a heat-proof bowl or jar to cool completely.
Chop cantaloupe into big chunks and toss into the blender. Blend until smooth. You should have about 1 ½ cups cantaloupe puree.
Put sea salt and cayenne pepper on a small plate. Brush a little simple syrup on the rim of the glass and place the glass into the mixture to coat rim.
In a shaker filled with ice, add ¾ cup cantaloupe puree, 1 oz. lime simple syrup, 1 ½ oz. tequila, and ½ oz triple sec. Shake well and pour into an ice-filled glass. Repeat for second drink.