How to Make It
Heat oven to 350° F. Spread the coconut on a rimmed baking sheet and toast, tossing occasionally, until golden, 6 to 8 minutes; let cool.
In a medium bowl, mix together the flour, baking powder, salt, and cooled coconut.
With an electric mixer, beat the butter and sugar on medium speed until creamy, about 3 minutes. Add the egg and vanilla extract and beat to combine. Reduce the mixer speed to low and gradually mix in the flour mixture just until combined (do not overmix).
Form the dough into two 12-by-1½-inch logs. Wrap them tightly in plastic wrap and refrigerate until firm, about 2 hours or up to 2 days.
Cut the logs into ⅜-inch slices and place on baking sheets, spacing them 2 inches apart. Sprinkle with sugar and bake, rotating the baking sheets halfway through, until golden, 9 to 11 minutes. Transfer the cookies to a rack to cool.
Storage suggestion: Keep the cookies at room temperature in an airtight container for up to 2 weeks.