1. Sprinkle gelatin over cold water in small saucepan; let stand for 5 minutes to soften. Place over low heat just until gelatin is dissolved.
2. In electric blender, blend raspberries at high speed until smooth, about 10 to 15 seconds. Add dissolved gelatin; blend 5 seconds longer.
3. Pour mixture into 8 x 8 x 2-inch metal pan; freeze until semi-set, about 1 hour. Place mixture in large bowl; using electric mixer at high speed, beat until smooth and fluffy.
4. Return mixture to pan; freeze until firm, about 2 hours.