Get out two glasses and set aside.
In a small bowl, squeeze the limes, no seeds.
In another small bowl, add a few tablespoons of salt.
Flip a glass upside down, and dip the rim of the glass into the lime juice, and then into the salt so it sticks.
Once you have enough salt on that glass, set it aside.
In the other glass, add about 3-4 slices of the jalapeño.
Use a muddler to mash the jalapeño. If you don’t have one, I use the stick that comes with my vitamix—just use anything to mash that jalapeño.
Next, add the tequila, the remaining lime juice, agave, and about 4 ice cubes.
Pour the margarita into the glass with the salted rim.
Add a few more ice cubes, and top with a cointreau/orange juice.