9x9x3 square cake baking

Hello, I am on my third attempt at baking a square 9×9×3 cake. I am using an aluminum pan, a bakers nail and the heating wrap around the outside. I have let it bake at 325 F for approximately 65-75 minutes. It always falls in the center. It holds approximately 6 cups of batter. Lastly, I filled the pan 1/2 full. Any suggestions would be appreciated. :) Thank you :)