Gluten-Free Sugar Cookies with Vanilla Buttercream

Ingredients

• 1 3/4 cups gluten-free all-purpose flour
• 1 1/2 teaspoons baking powder
• 1/2 teaspoon coarse salt
• 2 rounded tablespoons cornstarch mixed with 3 tablespoons water
• 1/2 cup unsalted butter or vegan baking stick, melted and cooled
• 1 1/4 cups plus 2 tablespoons granulated sugar, divided
• 1 1/2 teaspoons pure vanilla extract
• 1/4 cup plant milk (soy, almond, oat, etc.)
• 1/4 cup unsalted butter or vegan baking stick, at room temperature
• 2 1/4 cups powdered sugar
• 1 teaspoon pure vanilla extract
• 2 tablespoons water, at room temperature
• 1 drop red food coloring, optional
• 1/4 cup sprinkles, optional