In a medium bowl, whisk together flour, baking powder, and salt; set aside.

With electric mixer, beat butter and granulated sugar on medium-high until light and fluffy. Add the egg and vanilla and mix until combined. Reduce speed to low and add the flour mixture a little at a time until the dough comes together. Cover and refrigerate for 1 hour.

For each cookie, roll 2 tablespoons of dough into a ball. Place 2 inches apart on prepared cookie sheet. Using a serrated knife, cut three-quarters of the way down from the top of each ball. Repeat twice making three cuts to create six wedge-shaped petals. Use the tip of the knife to carefully spread the petals apart and open them slightly.

Bake 10 to 12 minutes, or until edges are lightly browned. They will still be pale, though. Cool on the baking sheet for 10 minutes, then move cookies to a rack to cool completely.

On low speed, mix the powdered sugar and meringue powder. Add the warm water. Increase speed to medium-high and beat until smooth and spreadable. Stir in the food coloring, adding color until it reaches the desired hue.

Set a cooling rack of cookies over a parchment-lined baking sheet. Spoon or baste icing over each cookie, letting it drip over the edges. I actually like using a basting brush to help get into the nooks and crannies.

Sprinkle the cookies with red sugar. Add a little more icing to the centers (if needed) and then attach the yellow candy pieces or sprinkles. Let cookies stand until the icing sets, about 1 hour.