In a measuring cup, mix the water and sugar. Add in the yeast and stir to combine. Set aside to proof for 5 minutes.
In a medium bowl, whisk together the flour mix, almond flour, whey protein, xanthan gum, and salt.
In the bowl of a stand mixer, add the proofed yeast, eggs, and melted butter. Add half of the flour mixture and mix on low speed for 30 seconds. Stop the machine and scrape down the sides.
Add the remaining flour mixture and mix again on low speed for 15 seconds. Scrape down the sides of the bowl.
Turn the mixer speed to medium and mix for 4 minutes.
While the dough mixes, prepare the filling by mixing brown sugar, cinnamon, nutmeg, and vanilla in a small bowl. Set aside.
Prepare a 9-10" Bundt cake pan by spraying well with cooking spray.
Pour half of the cake dough into the pan.
Spread the filling evenly over the cake dough.
Pour the remaining dough onto the filling, covering the entire surface. Use a spatula to cover it fully if needed.
Set the cake aside to rise for 35 minutes or until the cake dough rises by half. It will not double.
Preheat the oven to 375 F.
Bake cake for 30-35 minutes or until a toothpick inserted into the cake comes out clean.
Let cool in the Bundt pan on a wire rack for 15 minutes.
Place a serving plate on top of the pan and, in one motion, turn the cake pan upside down to release the cake onto the plate.
Let cool for 1 hour or until completely cooled.
In a small bowl, mix powdered sugar and almond milk, adding an extra Tablespoon of milk if needed.
Drizzle over the cake. Sprinkle with colored sugars if desired.
Notes
Use a gluten “bread” or high‑protein all‑purpose blend for better chew and oven spring.
Use a digital scale to measure the dry ingredients.
Use active dry yeast. It lets you proof the yeast in warm liquid first to confirm its activity.
Mix the dough for at least four minutes to combine all the ingredients.
Scrape the bowl well so no dry pockets remain.
Let the dough rise for 35 minutes, or until it rises by half.
Wait for the cake to cool before icing to help it stay fresh longer.
Apply colored sugars immediately while the glaze is wet so they adhere evenly.
Doneness CuesThe cake is ready when:
It is 190–200°F in the center.
The top and edges are an even golden brown.
A toothpick inserted into the thickest part comes out clean.
It springs back slightly when gently pressed.
The filling is ready when:
It is a set, slightly caramelized ribbon rather than a wet, syrupy layer.
The icing is ready when:
It is thick enough to coat the back of a spoon.
Storage
Room temperature storage: Store leftovers at room temperature in a sealed container or tightly wrapped for about 1 to 3 days.
Refrigeration: This can make the cake feel firmer or drier. But if your kitchen is very warm, wrap the cake tightly and refrigerate it in an airtight container for 4 to 5 days.
Freezing: Cool completely, wrap tightly in plastic wrap and, add a layer of aluminum foil. Then, place it in a freezer-safe container and store for up to 1 month.
Thawing: To thaw frozen cakes, leave them in the refrigerator overnight, then bring to room temperature before serving. For sliced cakes, thaw them at room temperature for several hours.