Preheat your oven to 350°F. Spray a 9x13 pan with cooking spray and set aside.
In a large bowl, whisk together the dry ingredients. Combine the egg, milk, oil and vanilla in a large measuring cup. Make a well in the center of the dry ingredients then pour the wet ingredients in. Mix until combined and there are no lumps in the batter.
Pour the batter into the pan and tap once or twice on the counter to remove any air bubbles. Sprinkle the cinnamon on top then using a knife swirl the cinnamon until it’s dispersed evenly on top of the batter.
Bake in the oven for 25-30 minutes or until a cake tester inserted comes out clean.
Remove and slice, serving while hot.
You can add blueberries, or other spices to this and customize it to your own liking!