Hello @jgikegami! We are so glad to hear from you again.
sorry to hear some of the tests did not go as planned. Yes, the batter would need to be baked or cooked before sealing, as the leavening produces gas and as the cake rises will displace air.
Yes, one option might be an apple-carrot pudding. To test baking in an approved oven use can, try contacting the manufacturer directly and request a sample of 100 stock cans, close to the size you plan to make, for product development testing. Take it one step at a time. When you have orders signed for the first 100,000+ cans you can easily risk MOQ.
in all likelihood my guess is that the can your contact is using has a liner in it that can only tolerate a little over 100° C, or the lining will melt. What if you tried to bake the cakes in the current cans, using a water bath? This will prevent the can from getting hotter than the contact water. Just an idea.
please do keep us informed of progress and questions!