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