In a blender combine raspberries, sugar, water, lemon juice, and moscato, if using. Blend on high speed until sugar is dissolved.
Strain sorbet base through a fine-mesh sieve set over a medium bowl. Cover with plastic wrap and refrigerate overnight. Alternatively, pour base into a large zip-top plastic bag and submerge in a bowl filled with ice water. Agitate the bag occasionally until chilled, about 30 minutes.
Taste the sorbet base and add a little more lemon juice if desired (the base should taste a little too sweet and tart, as the flavors will be less intense after freezing). Pour into an ice cream maker and freeze according to the manufacturer’s instructions.
Scrape the sorbet into a loaf pan, press a piece of plastic wrap directly on the surface, and freeze until solid, 8 hours or overnight.