Baking cake in one pan instead of splitting into two
That is highly unlikely to work in your case. Summing up all ingredients, I came to 1600 ml. I don't know what exact density cake has, but it is a foam full of air, so being twice as light as water seems plausible, which would make your single layer 3 inches high. And the pictures in the article pretty much agree with my guess, the cake pieces are 1.5 times as long as they are high. 

If you try to bake a 3 inch high cake layer, there is basically no time and temperature at which you can get it baked, you will always end up with a raw middle or with dust-dry, if not burnt, outer portions. 

If you insist making it a single piece, you may try a bundt pan instead of a cake pan. Alternatively, make half the recipe (assuming that your pan is indeed 9 inch - if it is 28 cm, you can make 2/3 of the recipe to get the same height) or really go with the two layers.