Red Velvet Cake - an American classic, this recipe from the book Sweet Tooth...

115g butter
280g caster sugar
2 eggs
1.5 Tbsp red food colouring (or not, if you don't want RED velvet)
325g flour
30g cocoa (I tend to use a bit more than this)
250ml buttermilk (or make your own from 250 ml milk and 1 tsp lemon juice/vinegar [remeasure before use])
1 tsp baking soda
1 tsp cider vinegar

Need: 2 18cm round cake tins, greased and lined.
Preheat: oven to 180C

Cream butter and sugar until light and fluffy and increased in volume (about 4 mins on an electric mixer).
Add the eggs gradually while still beating, then red food colouring. Beat until just incorporated.
Sift together flour and cocoa. Add half to the batter, beating until evenly mixed.
Beat in the buttermilk
Beat in the remaining flour mixture.
In a small bowl, mix the baking soda and cider vinegar (fizzzzzzz!), and fold immediately into the batter (by hand!)
Divide the mixture between the two tins, level to the edges, and bake 20-25 minutes until done.
Leave in tins for 10 minutes; turn out and cool complete.

Layer the cake with a cream-cheese icing, and ice as well. I usually mix cream-chease, icing sugar and a little vanilla and lemon, to taste.