Combine the strawberries and jalapeño pepper in a small blender and blend until smooth. Strain if you prefer but I’m lazy and usually don't bother. Pour the contents of the blender in a shaker.
Add the lime juice, agave nectar and tequila and a handful of ice. Secure the lid on the shaker and shake for 30-60 seconds to mix and chill the margarita
Strain the juice out and serve over ice with a splash of sparkling water
Notes
Instead of lining these margaritas with a salt rim, try combining equal parts salt and sugar for a sweet and salty rim! It's the best!