Carefully pour the hot lemonade syrup through a fine mesh strainer into a container to remove the lemon zest and any pulp. Cool to room temperature. Refrigerate or freeze the lemonade concentrate until ready to serve.
To make a pitcher of lemonade, fill the pitcher half way full of ice cubes. Add 1 cup of concentrate to a 32 oz. pitcher. Fill the pitcher with filtered water. Add some lemon slices to the pitcher and stir. Serve over ice.