For the Muffins• 1 ¾ cup all-purpose flour (220g)• ¾ cup granulated sugar (150g)• 2 Tablespoons cornstarch• 2 teaspoons baking powder• ½ teaspoon baking soda• ½ teaspoon table salt• ¾ cup sour cream (180g)• ½ cup unsalted butter melted (113g)• 1 large egg• 3 Tablespoons lemon zest• 2 Tablespoons lemon juice• ½ teaspoon lemon extract optional, but will give your muffins a stronger lemon flavor