In a bowl, add the brown sugar, white sugar, ground cinnamon, unsalted butter cubes, and almond flour. Using a spoon, give the ingredients a gentle mix.

Then, blend the ingredients until you have coarse crumbs using your hand, fork, or a pastry blender. I used both of my hands to work the butter pieces until coarse crumbs were formed.

Cover the streusel topping, and set it aside for later.

In a separate bowl, add the white sugar, brown sugar, ground cinnamon, and almond flour. Using a whisk, combine the ingredients and set the cinnamon filling mixture aside for later.

Preheat the oven to 180°C (356 °F)

In a bowl, add the white sugar, vegetable oil, egg, egg yolk, and vanilla extract. Using a stand-alone mixer or a hand-held mixer, at medium-high speed, combine the ingredients for 1-2 minutes until creamy and smooth. Then, slowly add the milk while mixing at a low speed. Adding the milk in intervals prevents the mixture from separating.

Then, in a separate bowl, add the white rice flour, tapioca flour, corn starch, brown rice flour, xanthan gum, baking powder, and salt. Afterward, whisk the ingredients to combine.

Now, add the flour mixture to the oil and egg mixture. Using a spatula, gently fold the flour mixture into the oil and egg mixture to combine. Try not to overmix the batter to limit the amount of air that gets incorporated.

Meanwhile, grease a 20 x 20 cm ( 8” x 8” inch) cake pan, and align it with parchment paper. Then, pour half of the coffee cake batter. Then add the cinnamon filling followed by the remaining cake batter. Finally, add the streusel topping, starting at the edges and moving towards the center.

Bake, the cinnamon coffee cake for 35-38 minutes, or until a toothpick inserted at the center, comes out clean.