Preheat your oven to 350°F (175°C). Line or grease a 9×9-inch baking dish and set aside.

In a large mixing bowl, whisk together almond flour, coconut flour, baking powder, and salt until evenly combined.

In a separate bowl, whisk the eggs until smooth. Add melted butter, heavy cream, granulated keto sweetener, and vanilla extract. Mix well.

Pour the wet ingredients into the dry ingredients. Using a spatula or whisk, mix until a smooth, thick batter forms. Let the batter rest for 2–3 minutes to allow the coconut flour to absorb moisture.

Pour the batter into the prepared baking dish and spread evenly.

In a small bowl, combine melted butter, brown-style keto sweetener, and cinnamon. Stir until fully mixed.

Spoon the cinnamon mixture evenly over the cake batter in lines or dollops.

Use a knife or toothpick to gently swirl the cinnamon mixture into the batter, creating a marbled pattern. Do not over-swirl.

Bake for 30–35 minutes, or until the center is set and a toothpick inserted comes out mostly clean.

Remove from the oven and allow the cake to cool slightly in the pan.

While the cake cools, prepare the icing by whisking powdered keto sweetener, heavy cream, and vanilla extract until smooth and pourable.

Drizzle the icing over the warm cake so it melts slightly into the surface.

Let the cake cool completely before slicing for clean pieces.