In a small bowl, combine dry ingredients (flour, baking powder, and salt). Set aside.
In the bowl of a stand mixer, combine butter and sugar. Beat until light and fluffy. Scrape down the sides of the bowl.
Add egg and vanilla bean paste (see note). Mix to combine. Scrape down the sides of the bowl.
With the mixer running on low speed, gradually add dry ingredients. Mix until just incorporated. Dough will be slightly sticky.
Turn dough out onto a lightly floured surface, and form into a ball. Cut dough in half, and form each half into a disk. Wrap dough in plastic wrap and chill for one hour.
After the dough has chilled, preheat your oven to 350F. Line baking sheets with silpats (see note) or parchment paper.
Working with one disk of dough at a time, roll the dough out to about ¼-inch thick. Cut out shapes as desired. Scraps may be gathered and re-rolled to cut more cookies. If dough becomes too difficult to handle, chill again in the refrigerator.
Place cut cookies on prepared baking sheets about 2 inches apart. Bake 15-17 minutes (see note) or until edges are lightly golden. Allow cookies to cool on the pan for 10 minutes, then remove to a wire rack to cool completely.
For Icing:
In the bowl of a stand mixer, combine water, meringue powder, and cream of tartar. With the whisk attachment, beat mixture until soft peaks form. Stop the mixer and scrape down the sides as necessary.
With the mixer running on low speed, gradually add the powdered sugar. Beat mixture until combined.
Color royal icing as desired. I outlined my cookies in royal icing. To frost the rest of the cookie, add enough water (you won't need much!) to make the icing a pourable consistency, and "flood" the cookies with the remaining icing.
Royal icing dries out quickly, so be sure to keep it covered with plastic or inside squeeze bottles (see note) if you're not using it right away.
If you'd like to create the "beach" design like I did, you need to have some white royal icing, then color the remaining royal icing blue and brown. Pipe brown and blue outlines on the cookies as desired.Take the remaining blue and brown royal icing and add enough water to each to make them a pourable consistency. Flood brown side with pourable royal icing, then sprinkle sugar on top to give the look of sand. Flood blue side with pourable royal icing.With the white royal icing, pipe squiggles (it's a technical term) where the sand meets the water. Using a small paint brush with a round tip, pull some of the royal icing into the "water" to give the look of surf.Enjoy!
Notes
Note on vanilla bean paste: The vanilla bean paste can easily be substituted with vanilla extract--BUT--these are simple cookies, and that little addition of the paste instead of extract makes a big difference in flavor! If you can't find it in your local grocery store (I never can), you can find it here. A little bottle lasts a long time!Note on using Silpat: I use silpats (like this one here) when baking, which makes the cookies brown up a little slower. If you're lining your pans with parchment (or just greasing them), your cookies will be done sooner.Note on bake time: Many variables will determine how long your cookies will take to bake. Cookies on parchment-lined baking sheets will brown faster than those on silpats. Dark pans will brown cookies faster than lighter-colored pans. Smaller cookies will be done more quickly than larger cookies. Keep an eye on them to ensure you're not over- or under-baking your cookies.Note on flooding cookies: I find that using squeeze bottles (like these here) to flood my cookies is much more convenient than trying to spoon it on.