There are a few options:

Baking Cores

Try the Wilton one
OR
Make your own by getting a steel can and removing both top and bottom – removing all traces of labels and glue – cleaning thoroughly. Once the batter has been placed in the prepared cake tin – place well-greased can upright in the middle. It acts like a heating core and it is a lot simpler to remove than the PROPER heating cores (which are not open at the bottom), and by putting in after the batter is in – the level of batter on the inside of the can is the same as the outside. The cooked cake is removed from the can and replaced into the hollow in the centre of the cake. Once covered it is virtually impossible to tell that anything was there.

Flower Nails

The ones you use to make buttercream flowers on, can be used in the base of the tin.
Just grease the flower nail and put it in the centre of your cake tin and pour the batter over it. Don’t forget to take the flower nail out before you decorate your cake.

Bake Even Strips

Two popular brands are Wilton and Maggi.
TIP: You don’t need to cut them to size, just continue wrapping
TIP: Rewet them to extend their life

OR

Home Made Baking Strips (the seemingly most popular choice as voiced by cakes and more cake friends)

Take a sheet of foil and place newspaper or paper towel in the centre (dampen how you see fit, some people run them under the tap before placing on the foil, I simply use a water spray) fold the foil and seal. Then wrap around the tin fastening with bulldog clips or paperclips to keep in place.

Cooking time may increase BUT level, evenly baked, moist cakes are the result.

Other members have tried using an an old towel cut into strips and folded in half lengthwise, wet it and wrap it around the tin before pouring in the batter.

The scientific explanation comes courtesy of cake friend Jules

“You are right about the even temperature across the cake – the edges cook faster as they are in contact with the tin/bakeware – this explains the volcano and cracking effect one can have with cakes as all surfaces cook faster than the middle – the middle of the cake needs to expand as it cooks and breaks thru the cooked cake causing the cracks. So if you are able to spread the heat more evenly we can achieve the perfectly flat cake and no humping – the drawback is no sampling as we don’t need to cut off the bump.”

Many cake friends have tried the home-made versions and many have been very surprised but also happy with the results. I believe the wet paper towel in the foil is one of the more popular ones to avoid that newspapery smell.

Sourced from Forum Member Contributions