A couple hours before you want to make the drinks, prepare the simple syrup so it has enough time to cool in the fridge. Combine the sugar, water and cayenne in a small saucepot and bring to a simmer. Stir so that all sugar melts then remove from heat and cool in the fridge.
To assemble the margaritas, run the lime wedge around the rims of the glasses then press in salt or spice rub. Place ice in glasses and add to each glass 2 oz tequila, 1 oz simple syrup (or to tastand 4 oz grapefruit juice. You can add more or less syrup and juice depending on how sweet you like your margarita. Stir well and serve.
**simple syrup will stay fresh for about a week in the fridge
This recipe from the kitchen of Eat Live Run, http://eatliverun.com