Combine rhubarb, sugar and water in a small saucepan and simmer until the rhubarb is softened and sugar has dissolved, about 10 minutes. Strain out the rhubarb and discard. Transfer syrup to an airtight container and chill until ready to use.

To make the margarita, combine tequila, triple sec, lime juice, rhubarb syrup and 2 jalapeno slices in a cocktail shaker over ice. Shake vigorously and then strain into an ice filled glass with rimmed with salt (optional) and garnish with additional jalapeño and lime slices.