How long do you bake 2 boxes of cake mix in a 9x13 inch pan?

When baking two boxes of cake mix in a 9x13 inch pan, you will need to adjust the baking time and temperature accordingly. Typically, you would bake a single box of cake mix in a 9x13 inch pan at 350°F for 30-35 minutes. Since you are doubling the recipe, you may need to increase the baking time by 10-15 minutes, but it's essential to monitor the cake closely towards the end of the original baking time to prevent over-baking. Use a toothpick inserted into the center of the cake to check for doneness - if it comes out clean, the cake is ready.