In a large mixing bowl, cream together softened unsalted butter and granulated sugar with an electric mixer until light and fluffy (about 2-3 minutes).

Beat in the large egg and vanilla extract until well combined. Scrape down the sides of the bowl.

In a separate medium bowl, whisk together the all-purpose flour, baking powder, and salt.

Gradually add the dry ingredients to the wet ingredients, mixing on low speed until just combined and a soft dough forms. Do not overmix.

Divide the dough in half, flatten each half into a disk, wrap tightly in plastic wrap, and refrigerate for at least 30 minutes (or up to 2 hours). This helps prevent spreading.

Preheat oven to 375°F (190°C). Line two baking sheets with parchment paper.

On a lightly floured surface, roll out one disk of chilled dough to about 1/4 inch thickness. Use a 2.5-3 inch round cookie cutter to cut out circles. Reroll scraps as needed.

Carefully transfer the cut-out cookies to the prepared baking sheets, leaving about 1 inch between them. Bake for 10-12 minutes, or until the edges are lightly golden. You may need to bake in batches, depending on your oven and sheet size.

Let the cookies cool on the baking sheets for 5 minutes before transferring them to a wire rack to cool completely. Repeat with the remaining dough.

In a large bowl, combine the sifted powdered sugar and meringue powder. Gradually add 1/2 cup warm water, mixing on low speed with an electric mixer until combined. Increase speed to medium-high and beat for 5-7 minutes, or until the icing is thick, glossy, and holds stiff peaks. If icing is too thick, add water 1 teaspoon at a time; if too thin, add more sifted powdered sugar.

Divide about 2/3 of the royal icing into a separate bowl. Tint this portion with orange gel food coloring until you achieve a vibrant basketball orange. Keep a small portion of the remaining white icing aside (about 2 tablespoons) for thinning if needed. Tint the remaining small portion (about 1/4 cup) of white icing with black gel food coloring.

Take about half of the orange icing and thin it with a few drops of water at a time until it reaches a "flooding" consistency (when you drizzle a spoonful back into the bowl, the line disappears within 10-15 seconds). This will be your orange flood icing. Do not thin the black icing as much; keep it at an outline consistency for piping details.

Fill a piping bag fitted with a small round tip (e.g., PME #2 or #3) with the thicker orange icing (outline consistency). Outline the edge of each cooled cookie.

Immediately fill another piping bag (or use a squeeze bottle) with the thinned orange flooding icing. Flood the outlined cookies, filling in the orange base. Use a scribe tool or toothpick to gently spread the icing to the edges and pop any air bubbles. Let the orange base dry completely (at least 1-2 hours, or ideally overnight) before adding black details. Drying time may vary based on humidity.

Once the orange icing is completely dry, fill a piping bag fitted with a very small round tip (e.g., PME #1 or #1.5) with the black icing (outline consistency). Pipe the classic basketball lines: one line across the middle, and two curved lines on either side, resembling a basketball seam.

Allow the black icing lines to dry completely, which usually takes another 1-2 hours, before stacking or storing the basketball cookies.