Whisk together white rice flour, sorghum flour, cornstarch, ginger, cinnamon, nutmeg, baking soda, salt, and xanthan gum in a large mixing bowl.Add pumpkin, eggs, oil, molasses, and golden syrup. Mix until ingredients are thoroughly combined and a smooth batter forms (use medium speed on a handheld mixer or medium-low speed on a stand mixer. If mixing by hand, use a balloon whisk and mix for two minutes). Scrape down sides and bottom of bowl once or twice with a rubber spatula while mixing.