Whimsical Butter Cookies with Royal Icing

Ingredients

• 1 cup unsalted butter, softened
• 1 cup granulated sugar
• 1 large egg
• 2 teaspoons pure vanilla extract
• 2 3/4 cups all-purpose flour
• 1/2 teaspoon baking powder
• 1/4 teaspoon salt
• 2 cups powdered sugar, sifted
• 1 large egg white or 2 tablespoons meringue powder plus 3 tablespoons water
• 1/2 teaspoon lemon juice
• Food coloring (pink, yellow, purple, blue, etc.)
• Edible glitter or sprinkles (optional)