I have never personally made a cake that looks like a turn table, but I have made lots of cakes in a variety of shapes and I think that a turntable will be very doable.
1. Start off by making a basic sponge cake mix, this is not only the quickest cake to make but also the easiest to work with.
The measurements of each ingredient depends on how big you want the cake to be. But just make sure that you have the same amount of butter, sugar and self raising flower, and 4 eggs to every 8oz of the other ingredients.
2. Pre-heat the oven to about 180 degrees and mix all of the ingredients together in a bowl. Grease one large, fairly flat cake tin, and two round ones, and pour the cake mix in.
3. Put all of the tins in the oven for about 20 minutes, or until they look a golden brown colour. Take them out and leave them to cool.
4. While the sponges are cooling, get some coloured royal or modelling icing. You will need the majority to be black. Roll out a large sheet of the black icing, enough to cover all three of the sponges.
5. Using a rolling pin to pick it up, and gently lower it onto the cool sponges so you can no longer see any sponge.
6. Pick up the two round sponges and place them side by side on the rectangle sponge, make sure there is a gap in between them both.
7. Now is the fun part, the decoration. This can be a bit more freestyle but I have found a few examples that you could try and copy the details from. However these have been done professionally so don't worry if yours doesn't look exactly the same!
These cakes also only have one turn style, so you could do this if you want the cake smaller and easier to make.