Prepare your pan. Preheat your oven to 375°F and spray a 9-inch round cake pan with nonstick cooking spray.
Combine the dry ingredients. In a large bowl, whisk together the flour, baking powder, ½ Tablespoon cinnamon, and salt.
Cream your butter and sugar. In a separate large bowl, use an electric hand mixer to beat together 4 Tablespoons (½ stick) butter and sugar until fluffy.
Add your wet ingredients. Beat in the eggs and vanilla before adding the milk.
Combine the wet and dry. Add the dry ingredients to the wet and mix until well incorporated.
Bake. Pour the batter into the pan and bake uncovered for 20-22 minutes or until a toothpick inserted into the center of the cake comes out clean.
Flip, garnish, and serve. Use a serving plate or cake stand to flip the cake out of the pan. While the cake is still warm, spread 4 Tablespoons of butter over the top. Sift powder sugar over the cake and sprinkle with the remaining cinnamon. *See notes. Serve room temperature or slightly warm.
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Notes
Bake Time: Some have found that baking this cake for 30 minutes is ideal. However I find it's too dry when it bakes that long. Baking for 21 minutes in my oven is perfect.
Cinnamon Topping: You may not need the remaining ½ tablespoon of cinnamon to sprinkle on top. I'll usually just sprinkle on 1 teaspoon but it's your preference.