In a small saucepan combine 1 cup granulated sugar and 1 cup water. If using, add 1 tablespoon lemon zest to the pan to infuse citrus oils. Bring mixture to a gentle simmer over medium heat, stirring frequently until the sugar is fully dissolved (about 3–4 minutes). Do not boil vigorously — a gentle simmer is sufficient.

Cool and strain

Remove the pan from heat and let the syrup cool for 10–15 minutes. If you used lemon zest, strain the syrup through a fine-mesh sieve into a heatproof container to remove zest. Allow the syrup to cool completely to room temperature before using. Refrigerate any extra syrup in a sealed container for up to 2 weeks.

Lemonade

Juice the lemons

Roll the lemons on the countertop under the heel of your hand to soften them. Cut lemons in half and juice until you have 1 cup fresh lemon juice (about 4–6 medium lemons). Strain the juice through a fine mesh sieve into a measuring cup to remove seeds and excess pulp if you prefer a clearer lemonade.

Mix the lemonade

In a 2-quart pitcher combine 1 cup fresh lemon juice, 1 cup cooled simple syrup, and 4 cups cold water. Add a pinch of salt if using to round flavors. Stir thoroughly and taste. Adjust sweetness or tartness: add up to 1/2 cup more simple syrup for sweeter lemonade, or up to 1 cup more water for milder flavor.

Chill and serve

Add 4 cups of ice to the pitcher or divide ice among glasses. Pour the lemonade over the ice. Garnish each glass with lemon slices and a sprig of mint if desired. Serve immediately. Leftover lemonade can be refrigerated up to 5 days; stir before serving as separation may occur.