Puree 2 cups chopped strawberries in a food processor until smooth, about 30 seconds.
Pour puree through a fine-mesh sieve into a large bowl discarding seeds.
Add buttermilk, sugar, cinnamon, lemon juice and vanilla to the puree.
Stir until blended.
Cover and chill for at least 2 hours or up to one day.
Pour mixture into 1 1/2 quart freezer container of ice-cream maker.
Freeze according to manufacturer's instructions adding remaining 1 cup chopped strawberries during the last 2 minutes of churning if desired.