To get nice high sided cakes (you need 3 inches for carving Lindy’s wonky cakes) try wrapping the outside of the cake tin with newspaper (just like you would for a fruit cake). This slows down the cooking of the outside of the cake allowing time for the sides to reach the right height. You may find that this increases the total cooking time by 5 to 10 minutes but just keep checking the cake near the end of the cooking time to see when it’s done. Don’t forget you can cover the top with a loose bit of foil if the top of the cake starts browning too much
A tip for baking deep Madiera cakes
Another tip with Madeira cakes is to create a hollow in the middle of the mixture before baking. You can literally leave virtually nothing in the middle of the tin, pushing it all out to the sides. This will give you a lovely flat cake rather than domed. Unfortunately, you can’t really do it with the chocolate cake mix as it’s slightly runnier and doesn’t stay where you put it!
Hope these tips help