How to Bake a Flat Cake

I was interested to learn that the reason cakes rise in the middle causing a dome affect, is that the cake cook quicker on the outside than the middle.  The internet advised me to find an old towel, cut it in half, soak and pin around the tin while it cooked.  This worked, but, I burned my finger on the safety pin and my cake sank as soon as it came out of the oven.

Before

After

I then had to look on the internet for why cakes sink and it turns out there are a lot of reasons.  In this case I think I should have cooked it longer.