Buttermilk is a useful low-fat staple; it gives this ice cream a creamy, tangy taste.
Quarter nectarines; remove and discard pits, but do not peel. Place in a food processor and puree until smooth, about 1 minute. Transfer to a medium bowl, and add sugar, corn syrup, lemon juice, and ginger. Whisk to combine, cover, and let stand for 1 hour.
Pass nectarine mixture through a fine strainer into a medium bowl, discarding solids. Add buttermilk and half-and-half, and whisk to combine. Transfer to an ice-cream maker, and freeze according to manufacturer's instructions. If necessary, do this in two batches, keeping remainder of ice cream refrigerated while the first batch is freezing.