Combine 1 cup water and 1 cup granulated sugar in a small saucepan over medium heat. Stir until the sugar dissolves and the mixture comes to a gentle simmer.

Add the 2 tbs dried culinary lavender and the optional 1 tsp lemon zest to the simmering syrup. Reduce heat to low and simmer gently for 3 minutes to infuse the lavender without extracting too much bitterness.

Remove the pan from heat and let the lavender steep in the syrup for 15 minutes, covered to retain aroma.

Strain the syrup through a fine mesh strainer or cheesecloth into a heatproof container, pressing lightly on the lavender to extract syrup but not the bitter solids. Discard solids. Let the syrup cool to room temperature (about 20–30 minutes) or chill in the refrigerator for faster use.

Lemonade Base

While the syrup cools, juice fresh lemons until you have 1 cup of lemon juice (about 4–6 medium lemons). Strain seeds and excessive pulp if desired for a smoother drink.

In a large pitcher, combine the 1 cup fresh lemon juice with 2 cups cold still water. Add 1/2 to 3/4 cup of the cooled lavender syrup to start (adjust to taste). Stir well and taste for balance: add more syrup if you want sweeter and more lavender-forward.

Add 2 cups of ice to the pitcher to chill the mixture and slightly dilute for balanced acidity.

Sparkling & Finishing

Just before serving, add 2 cups chilled sparkling water or club soda to the pitcher and stir gently to preserve carbonation.

Add 1 tsp fine sea salt to the pitcher and stir until dissolved. Salt should be added sparingly — it brightens flavor and rounds acidity. Taste and adjust: add up to another 1/4 tsp if needed, or more syrup if too salty.

Pour lemonade into four tall glasses over additional ice, making sure to leave some space for garnish and bubbles.

Garnish each glass with a lemon slice and an optional fresh lavender sprig. Serve immediately so the sparkling water remains fizzy.