Step 1: Clean the Orange
First thing you do is cut a small circle at the top of the orange. Then using a spoon (preferably metal, we only had plastic on this camping trip) scoop out all the guts. Having a little bit left over is okay it won't affect the taste at all. It will actually help the taste. :-)
Step 2: Mix the Cake
Next using your favorite cake mix, mix your cake batter. Then fill your orange about half full. I recommend choosing something that will be good with a hint of orange flavor. In this instructable we chose yellow cake. It's also important to know that you're doing this while camping so using a cake mix that's easy to mix while you're camping is a good idea.
Step 3: Cook the Cake
Place the top back on the orange and then wrap it in two layers of tinfoil. It's important to use two layers. Then place it in a nice spot in the fire. We call this cooking coals. We cooked ours about 15 minutes. I recommend checking it after 10 as there's no guarantee of temperature when you're cooking.
Step 4: Eat the Cake
Okay, you've checked the cake and it's nice and fluffy most likely it's coming out the top some. That means it's ready. So take the top off and start eating!