How to Make It
Combine ginger, sugar, and ½ cup water in a small pot over medium-high. Bring to a simmer and cook, stirring occasionally, until sugar dissolves, about 5 minutes. Let cool slightly, then strain. Discard ginger.
Combine pineapple, ginger syrup, and lime juice in a food processor and process until smooth. Transfer to an 8-by-8-inch baking dish and spread into an even layer. Freeze until firm, about 4 hours. Remove from freezer and rake with a fork. Cover with plastic wrap and return to freezer for at least 1 hour or up to 1 week.
Top with salt and serve with lime wedges.