Combine the first 4 ingredients in a medium saucepan. Bring to a boil over medium-high heat, and cook for 1 minute or until sugar dissolves.
Place sugar mixture and raspberries in a food processor, and process until smooth. Press the mixture through a fine sieve over a large bowl, and discard seeds. Cool completely.
Pour mixture into the freezer can of an ice-cream freezer, and freeze according to manufacturer's instructions. Spoon sorbet into a freezer-safe container; cover and freeze 1 hour or until firm. Remove sorbet from freezer 10 minutes before serving.