Preheat your oven to 400°F. Spray a 9-inch nonstick round cake pan with cooking spray, or alternatively, grease it with butter or line it with parchment paper if you prefer. In a large bowl, crack the 4 eggs and add the maple syrup, then whisk them together until well combined. Add the almond flour and baking powder to the egg mixture, stirring with a spoon until fully incorporated. Gently fold the blueberries into the batter. Pour the batter into the prepared pan, spreading it evenly. Bake at 400°F for 30 minutes, or until the top turns a golden brown. Once done, remove the cake from the oven and let it cool in the pan for at least 5 minutes before slicing.