Preheat the oven to 375ºF and prepare two large baking sheets with parchment paper.
Use a mixer with beaters or a stand mixer with the paddle attachment to beat the butter and brown sugar together until light and fluffy. If you don't have an electric mixer, use a wooden spoon or your hands to ensure the sugar gets dissolved.
Beat in the molasses, vanilla extract, and egg.
Place the gluten-free flour, baking soda, spices, and salt in the bowl. Lightly stir them together on top, then gently mix together until there are no dry spots. The dough will be slightly sticky.
Use a 3 tablespoon cookie scoop to scoop the dough, one at a time. Place the scoop of cookie dough in a small bowl filled with the white sugar. Gently roll the dough ball until it is fully coated in sugar. Place on a parchment lined baking sheet and gently push down to flatten it slightly. Repeat with all the cookie dough.
Bake the cookies for 10-15 minutes until the edges are firm and they are starting to crack on top. For super soft cookies, bake for the lower end of the time range. For perfectly round cookies, take a large cookie cutter or the top of a glass and gently run it around each cookie immediately after removing it from the oven. This will reinforce a circular shape as the cookie cools.
Allow the cookies to cool on the baking sheet for 15 minutes until they have set, then transfer to a wire rack to continue cooling. Enjoy warm or allow to come to room temperature.