This blueberry coffee cake is one of the best baked goods I've ever made. It is melt-in-your-mouth good. I think it helps that it uses almond and coconut flour plus Greek yogurt for a lighter and higher moisture level. And even though the crumb topping is using non-traditional flours and is sugar free, the whole coffee cake still tastes legit like something you might buy at a bakery.
Line a cake pan with parchment paper and set aside. I used an 8x8 square pan.
Add the first 4 ingredients to a bowl and whisk together to break up any lumps in the flour.
In a separate bowl, add the butter and sweetener and beat together until creamy.
Add the remaining cake ingredients (except the blueberries) to the butter mixture and beat again until incorporated. Fold in the dry mixture and stir well. Set aside.
In another bowl, add all the ingredients for the crumb topping. Use a fork to incorporate it all together.
Add the cake batter into prepared pan. Note: It will be thick and will not pour. You will need to use a rubber spatula to spread it out in the pan.
Spread your blueberries around the top of the batter. Then, using clean hands, crumble the crumb topping over the blueberries.
Bake for 40 minutes. Let cool completely and enjoy!