Step 1 Puree the raspberries in a food mill, discarding the seeds. The raspberries can also be pureed in a food processor, then strained to remove the seeds. This makes about 1 cup puree.
Step 2 Place the berries in a medium bowl and whisk in the sugar until dissolved. Stir in the lemon juice and chill until ready to use. This makes a scant 1 1/2 cups syrup and will keep for 3 days, covered and refrigerated.