Prepare the dough: In a mixing bowl, combine instant yeast, 1 tbsp sugar, and warm milk. Mix well, cover with a kitchen towel, and let it rest for 10-15 minutes until bubbly. Set aside.

In a standing mixer bowl, mix gluten-free bread flour, xanthan gum, the remaining 3 tbsp sugar, and baking powder. Whisk all dry ingredients until fully incorporated.

Add the large eggs and pour in the yeast mixture. Attach the hook to the standing mixer and mix for 10-15 minutes. Add more milk if the dough appears too dry.

Once the dough is smooth, add the unsalted butter and salt. Mix again until the dough is uniformly smooth.

Transfer the dough to a floured flat surface. Knead for 5 minutes, then form it into a ball. Place the dough in an oiled clean bowl, cover with a damp kitchen towel, and let it rest for 40-45 minutes, or until it has doubled in size.

Prepare the cinnamon filling: Combine brown sugar, cinnamon powder, gluten-free all-purpose flour, unsalted butter, vanilla extract, and chopped apple. This mixture can be refrigerated until ready to use.

When the dough is ready, transfer it to a flat surface covered with parchment paper. Place another sheet of parchment paper over the dough and roll it into a ¼-inch thick rectangle. Position the longer side closest to you for easier rolling.

Spread the cinnamon sugar mixture evenly over the dough, leaving a 1-inch clean border. Using the parchment paper, roll the dough into a log, then securely pinch the seam and ends closed.