1 12-ounce package frozen unsweetened raspberries (about 3 cups)
1 cup sugar
1/2 cup water
1 1/2 tablespoons grated lemon peel
1 cup fresh lemon juice
1 1-liter bottle (33.8 ounces) chilled sparkling water or club soda
Fresh raspberries (optional)
1. Combine frozen raspberries, sugar, and 1/2 cup water in medium saucepan. Stir over medium heat until sugar dissolves and berries thaw. Increase heat and boil 3 minutes. Strain raspberry mixture into bowl, pressing on solids to extract as much liquid as possible; discard solids in strainer. Mix lemon peel into raspberry syrup in bowl. Chill until cold.
2. Stir raspberry syrup, lemon juice, and sparkling water in large pitcher to blend. Fill 6 glasses with ice cubes. Pour raspberry lemonade into glasses. Add fresh raspberries to each glass, if desired. Garnish with lemon slices and serve.