For the cake, start by adding the almond flour, coconut flour, salt, baking soda, and ½ Tbsp of the cinnamon in a large bowl. Whisk to combine, then set aside.
In a small bowl, add the eggs, powdered stevia, and the remaining 1 Tbsp of cinnamon, and whisk until frothy. Add yogurt, then stir to combine.
Add the liquid ingredients to the dry ingredients. Stir to thoroughly combine. Spoon your cake batter into a prepared pan, then evenly sprinkle with crumb topping.
Bake the crumb cake for 20 minutes or until center is firm to the touch. Cool, and serve!