To make the cookies: Weigh your masa harina; or measure it by gently spooning it into a cup, then sweeping off any excess., In a large bowl or bowl of a stand mixer, whisk together the masa harina, sugars, baking powder, cinnamon, and salt., Add the butter, egg, water, vanilla, and zest all at once. Using a flexible spatula or the flat beater attachment of the stand mixer, stir to combine all the ingredients. The dough will resemble wet sand., Working in the bowl, gently knead the dough to form a smooth, cohesive mass, about 1 minute., Form the dough into a disk about 6" in diameter. Cover with plastic wrap or your favorite reusable wrap and let the dough rest for 30 minutes at room temperature. (This allows the masa harina to fully hydrate.), While the dough rests, place racks in the upper and lower thirds of the oven and preheat to 400°F. Line 3 baking sheets with parchment., Lightly dust your work surface and a rolling pin with masa harina. Roll the dough to 1/2" thick (roughly 13" x 8"); the cookies will spread in the oven. If the dough begins to crack, that’s OK; simply press or pinch it back together., Cut the dough into 2 1/4" circles and transfer to the baking sheets, spacing about 3" apart., Re-roll the dough scraps and cut out additional cookies., Starting with 2 of the sheets, bake the orange sugar cookies for 10 to 13 minutes, rotating the pans on the racks from top to bottom halfway through baking. The cookies are done when they are lightly golden brown around the edges., Remove the cookies from the oven and allow them to cool on the pan for 5 minutes before transferring them to wire racks to cool completely., Bake the final sheet of cookies in the top third of the oven for 10 to 13 minutes for best results., To make the glaze: In a medium bowl, whisk together the confectioners’ sugar, orange juice, melted butter, and salt. Slowly add more juice, 1 teaspoon at a time, until the glaze is the consistency of thick maple syrup., Set the wire racks of cookies over parchment-lined baking sheets. Dip the top of each cookie in glaze or spread the glaze across the tops of the cookies with a small offset spatula. Set the cookies aside until the glaze has set, about 30 minutes., Storage information: Store leftover orange sugar cookies in an airtight container at room temperature for up to 3 days.