In a large bowl, whisk together all-purpose flour, almond flour, baking powder, kosher salt, and ground cinnamon.
In a separate large mixing bowl, vigorously whisk eggs. Add sugar, melted butter, and vanilla extract, then whisk until thoroughly mixed.
All at once, pour in the dry ingredients, then use a rubber spatula to gently fold them into the wet ingredients. Fold again gently until just mixed, then pour out into the prepared cake pan.
Transfer the cake to the preheated oven then bake until a cake tester inserted into the center of the cake comes out clean. *If the cake begins to brown too quickly, you can cover it with aluminum foil.
If serving warm, allow the cake to cool in the pan, then transfer to a platter by inverting first onto a plate, then back onto the platter. Dust with powdered sugar, then slice and serve. Enjoy!