All you need are just a few ingredients like a box cake, fresh peaches, and vanilla extract to make this delicious peach upside down cake, using your slow cooker!
Spray your slow cooker HEAVILY with nonstick spray or rub down with butter or oil.
Add the melted butter to the bottom of the slow cooker and sprinkle over the brown sugar. Mix lightly with a spoon and spread out evenly over the bottom of your slow cooker.
Lay down the peach slices top of the brown sugar mixture.
In a medium sized bowl add the cake mix, water, eggs, oil and vanilla. Mix with a spoon until combined, do not overmix or try to remove the lumps.
Pour the batter over the peaches in the slow cooker.
Place the lid on the slow cooker and cook on HIGH for 2 hours. If your slow cooker cooks hot, it may be a little less time. You know your cake is done when the cake is set in the center.
Remove the insert to a cooling rack when the cake is done. Let cool for about 20 minutes before attempting to turn over onto a platter or cutting board.
Flipping the cake on to a platter or cutting board works best with two people if possible.
Notes
For the best peach cake, I recommend using ripe peaches. Canned peaches will not hold up as well since they have been in syrup for a while. I also recommend that you not use frozen peaches.
Place any remaining cake in an airtight container. It can be kept on the kitchen counter but eaten within 2-3 days. If you want to last a bit longer, put it in the fridge.