Dissolve the yeast in the warmed milk beverage, and let sit to proof. It should foam a bit. If it doesn't your yeast may be inactive.
In a large bowl, combine the flours, sugar, baking powder, and salt.
Stir the milk beverage mixture, applesauce, egg or egg alternative, vinegar, and stevia (if using) into the flour mixture. Mix well, until very smooth.
Pour the batter into your prepared pan and let rest for 15 minutes.
Cinnamon Sugar Topping
While the dough rests, mix together the brown sugar, melted buttery spread, and cinnamon in a small bowl.
Pour the mixture evenly on top of rested dough and swirl it in with a spatula.
Place the pan into a cold oven, then set the oven temperature to 350ºF.
Bake for about 30 minutes, or until the cinnamon bun bread is lightly browned at the edges and the center of the bread springs back when lightly pressed. Some of the sugar mixture on top may still be bubbling.
Let cool for at least 30 minutes before cutting the bread into thirds each way, to make 9 squares.
Icing
In a bowl, whisk together the powdered sugar and water until smooth.
Serve the cinnamon bun bread slices warm with the icing drizzled over top. Leftovers can be reheated in the microwave.
Notes
*If you do eat wheat, feel free to swap in 1½ cups of all-purpose flour for the white rice and gluten-free all-purpose flours. **If you don't wish to use stevia, omit it, increase the sugar to ⅓ cup and add ½ teaspoon vanilla extract with the wet ingredients.
Recipe by Go Dairy Free at https://www.godairyfree.org/news/nutrition-headlines/cinnamon-bun-bread-for-the-gluten-free-dairy-free-and-low-sugar