Preheat oven to 350F and line an 8×8 pan or 8-inch round cake pan with parchment paper or nonstick spray.
In a medium sized bowl, mix together almond flour, baking soda, cinnamon, and salt. In a larger bowl, whisk together eggs, protein shake, maple syrup, and vanilla. Add dry ingredients to wet and stir to combine. Pour into baking dish.
In small bowl, mix together the crumb topping completely. Sprinkle it over top of the cake batter until evenly dispersed.
Bake in oven for 25-30 minutes or until toothpick inserted in certain comes out clean. Let cool at least 30 minutes before serving. Optional, sprinkle with powdered sugar. Store on counter for 24 hours or longer in fridge.
Note: Be sure to watch this when cooking. Loosely cover the bars with aluminum foil around the 15 minute mark. The foil prevents the top from getting too brown.