To a small bowl or cup, add 1/2 tablespoon of butter and melt in the microwave. Stir in the dark brown sugar and cinnamon; set aside.
Melt the 2 tablespoons of butter in the mug, in the microwave. Swirl the melted butter around the mug to coat the sides and transfer the remaining to a small bowl.
Add the 1-1/2 tablespoons granulated sugar and milk to the melted butter. Microwave again just until warm; stir and set aside.
In a separate bowl, whisk together the flour blend, flaxseed meal, baking powder, yeast, and salt; add to the milk mixture and whisk until smooth and slightly thick, about 1 minute.
Reheat the cinnamon filling for a few seconds until it melts. Add one-third of the dough-batter to the prepared mug. Top with a little less than half of the cinnamon-sugar mixture. Repeat. Add the last third of the dough and top with a tiny bit of the remaining cinnamon mixture. Set aside in a warm environment (80 - 86ºF). (A preheated toaster oven that has been turned off works well or a dough proofer.)
Microwave on high for 1 minute. If the cinnamon roll falls when the 1 minute is over, microwave for an additional 10 seconds (based on a 1200-watt microwave). Do not overcook or it will result in a gummy cinnamon roll. Set aside to cool to room temperature, about 25 minutes.
Whisk together the glaze ingredients. Immediately, prior to cooling completely, top the cinnamon roll with the glaze.