Red Velvet Whoopie Pies

Ingredients

• 8 tablespoons (1 stick) unsalted butter, at room temperature
• 1 cup granulated sugar
• 1 large egg, at room temperature
• 1 teaspoon pure vanilla extract
• 1 ounce red food coloring (about 2 tablespoons)
• 2 cups sweet rice flour blend
• 2 tablespoons unsweetened cocoa powder
• 1/2 teaspoon kosher or fine sea salt
• 1/2 cup buttermilk
• 1/2 teaspoon apple cider vinegar
• 1/2 teaspoon baking soda
• 6 ounces cream cheese, at room temperature
• 3 tablespoons unsalted butter, at room temperature
• pinch of kosher or fine sea salt
• 1 teaspoon pure vanilla extract
• 3 cups confectioners' sugar