Capture the pure flavor of fresh raspberries in this simple sorbet.
Place fruit and water in a food processor, and process until very smooth. Pass through a fine sieve into a deep bowl or a large glass measuring cup, pressing on solids with a flexible spatula to extract as much liquid as possible. Don't press too hard, or some of the seeds (if there are any) may be forced through the strainer into the liquid. Discard any solids that remain in the strainer.
Transfer strained puree to a deep bowl or plastic storage container. Add simple syrup (start with 1/2 cup syrup, then add more as needed) and stir until it is well combined. (To determine whether you need more syrup, gently drop a just-cleaned and dried egg into puree and push to submerge completely; when the sugar content is right, a piece of egg about the size of a quarter should be exposed. If the egg doesn't float to the top, add more syrup; if too much egg is exposed, add more fruit puree.) Cover bowl or container, and refrigerate until completely chilled before using, at least 1 hour (or overnight).
Pour mixture into an ice-cream maker and freeze according to manufacturer's instructions. Transfer sorbet to a large airtight container; freeze at least 2 hours (or overnight) before serving.