Prep your oven and pans. Position a rack in the center of the oven and preheat the oven to 350°F. Line two half sheet pans with parchment paper.
Make the cookie dough. In a medium bowl, whisk together the flour, baking powder, and salt.
In the bowl of a stand mixer fitted with the paddle attachment, combine the sugar and butter. Beat on medium-high until light, fluffy, and doubled in volume, 3 to 5 minutes. Reduce the mixer to low and add the egg; beat until just combined. Use a rubber spatula to scrape down the bottom and sides of the bowl. With the mixer on low, add the ube halaya jam, purple food coloring, ube extract, and vanilla extract, beating until combined and completely purple, 1 to 2 minutes. Gradually add the dry ingredients and beat until just combined. Scrape down the bottom and sides of the bowl once more, and beat on low for an additional 30 seconds. Coat the cookies. Place the confectioners' sugar in a medium, shallow bowl. Use a 3-Tablespoon cookie dough scoop to portion the cookie dough into balls, dropping them directly into the bowl with confectioners' sugar. Toss until the cookie dough balls are completely and generously coated. Place the cookie dough balls at least 3 inches apart on the prepared sheet pans.
Bake the cookies. Bake one pan at a time for 12 to 15 minutes, or until the edges have set but the centers are still soft.
Serve and store. Serve warm, or at room temperature. The cookies can be stored in an airtight container or zip-top bag at room temperature for up to 3 days.