Bring mixture to a gentle simmer, stirring occasionally to dissolve the sugar. Simmer 6–8 minutes until blueberries have softened and released juices.

Use a muddler or the back of a spoon to gently crush the berries in the saucepan to release more flavor and color.

Add lemon zest and cook 1 more minute, then remove from heat. Stir in fresh lemon juice.

Strain the syrup through a fine-mesh sieve into a heatproof container, pressing solids to extract as much liquid as possible. Discard solids or reserve a few spoonfuls for garnish.

Cool syrup to room temperature, then chill in the refrigerator. Syrup will keep up to 2 weeks refrigerated.

Cocktail Assembly

Prepare the glass: rub the lime wedge around the rim of a rocks or coupe glass. Dip rim into coarse salt or sugar to coat evenly; set glass aside.

In a cocktail shaker, add blanco tequila (2 oz), triple sec (1 oz), fresh lime juice (1 oz), sour mix (1/2 oz), and blueberry lemon-zest syrup (1 oz). If you prefer a sweeter drink, add simple syrup to taste (start with 1/4 oz).

Add ice to the shaker until nearly full (about 1 cup). Secure the shaker lid and shake vigorously for 12–15 seconds until the shaker is well chilled and slightly frosted.

Strain the cocktail into the prepared glass over fresh ice (if using a rocks glass) or neat into a chilled coupe.

Garnish with 4–6 fresh blueberries skewered or dropped into the drink and a small strip of lemon zest expressed over the top to release oils, then placed on the rim.

Serve immediately.