Trim off top of jalapeno and cut in half lengthwise.
Place sugar, water, and sliced jalapeno in a pot. Bring to a boil, stirring constantly.
Reduce heat to a simmer and continue cooking for 12 minutes.
Strain pepper and seeds from mixture. Allow to cool and refrigerate.
Cut limes in half and squeeze as much juice from them as possible.
If using lime for garnish, cut one lime into wedges.
Refrigerate lime juice and wedges until ready to use.
Combine lime juice and jalapeno simple syrup in equal parts (1:1).
Do this 2-24 hours in advance of serving to allow flavors to meld. Refrigerate until ready to use.
Combine 2 parts margarita mixture to 1 part tequila (add more tequila to taste).
Pour over ice and enjoy!