In a small or medium saucepan, heat the butter over medium temperature, stirring or swirling the butter in the pan continuously until the milk solids start to separate and begin to brown. Remove from the heat and pour into a small bowl to cool.
In a medium bowl combine the rice flours, tapioca, cornstarch, baking soda, cinnamon, and ¼ teaspoon salt.
In a stand mixer bowl, or in a bowl with a hand mixer, cream together the sugars, molasses or honey, egg, vanilla, and optional rum.. Add the cooled butter and continue to mix together until smooth. Add the flours to the creamed mixture and beat in. Add the oats, nuts, chocolate chips, and dried fruit if using. Mix on low to combine.
Cover and chill for 1 ½ -2 hours.
Preheat the oven to 350 degrees.
Line a stone baking sheet or a cookie sheet with parchment paper. Use a scoop or scoop by heaping tablespoons, placing the cookies 2 inches apart on the sheet.
Bake one tray at a time for 10 minutes. Add a few crystals of Morton’s Salt to the top of each and continue baking another 2-3 minutes, until the cookies are beginning to brown slightly.
Remove from the oven. Let the cookies sit on the tray for 2 minutes before removing with a spatula to a wire rack to finish cooling.
