I have a muffin recipe for chocolate zucchini muffins. The recipe calls for a 325 degree oven and a baking time of 20-25 minutes. I want to bake these in a 9 x 13 pan as a cake. How long should I bake my cake and at what temperature.
Most of the bake times that recipes give you are very general ideas of how long you should bake something. This is why most of them are given in ranges rather than in specific values. (20-25 minutes instead of specifically saying 21 minutes)
The reason for this is because there are a lot of variables when it comes to baking including the thickness and material of your pan and the type of oven you have.
The best thing to do when you are trying to bake batter for muffin/cupcake in a cake pan is to start out with the initial time the recipe gives you and then there after, check it periodically with a toothpick in the center. If the batter sticks to the toothpick then it is not done. You can check it every 5 minutes to start off but as the "cake" start to stick less to the toothpick, check more often.
As you know that the muffin dough is always thicker than the cake dough. In this case I am not clear if you are changing the recipe thinning it or not. If you are only considering the size, then of course you have to increase the time, adding from 5-10 minutes. The temperature is usually 325 for most of the cake and muffin baking options. I bake my cake (cake or muffin recipe) for 30-35 minutes. Be confident for 30 minutes and then start to observe.
Hope it helps....
I would raise temperature up to 350° and start by putting it in for 30 minutes and check it every 5 minutes after that. I did something similar a while back and my cake took 50 minutes to bake. Since muffins are smaller, it takes less time for the heat of the oven to reach the centre of the muffin to bake it, which is why cake takes longer.