Pineapple Cilantro Serrano Cocktail

Ingredients (6)

• 1 tablespoon fresh cilantro
• 1/2 small lime, juiced
• 1 small, round slice of serrano pepper (1/8th to 1/4th-inch thick)
• 1 1/2 ounces silver tequila
• 3 ounces quality pineapple juice
• agave nectar (optional), to taste