How to Make It
Preheat oven to 300°F. Stir together flour, baking powder, salt, and baking soda in a small bowl. Beat sugar, eggs, and vanilla in a large bowl with an electric mixer on medium speed until thick and pale, about 2 minutes. Stir in flour mixture, coconut, cherries, and orange zest. (Dough will be very sticky.)
Turn dough out onto a heavily floured surface; knead lightly 8 or 9 times. Shape dough into a 15- x 3-inch loaf, and place on a parchment paper-lined baking sheet; pat to 3/4-inch thickness.
Bake in preheated oven until loaf is golden brown, about 40 minutes. Cool on pan on a wire rack 5 minutes. Cut loaf diagonally into 22 (1/2-inch-thick) slices. Place slices in a single layer on same parchment paper-lined baking sheet, and bake 20 minutes, turning slices over halfway through baking. Remove from baking sheet; cool biscotti completely on wire rack, about 20 minutes.