Stir together water and 1/4 cup sugar until sugar dissolves.
Pulse raspberries in a food processor until coarsely chopped. With machine running, pour in sugar-water; pulse until mixture is smooth. Transfer to an airtight container, and freeze until firm, about 30 minutes.
Whisk cream and remaining tablespoon sugar until soft peaks form.
Scoop sorbet into 4 glasses, and top with whipped cream.