In a small saucepan, bring sugar and water to a boil; remove from heat. Refrigerate for at least 1 hour, or until chilled.
In a large bowl, whisk together buttermilk, lemon juice, corn syrup, and salt. Slowly add chilled syrup; whisk to combine. Stir in lemon zest. Freeze in an ice-cream maker according to manufacturer's instructions.
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