This is from Marian Keyes' Saved By Cake. Delicious and very easy (if not the cheapest cake to make!)

100g dark (70%+) chocolate
250g self-raising flour
1 tsp baking soda
1 tsp salt (seems a lot!)
250g caster sugar
125ml sunflower (or other non-flavoured; I used grape-seed) oil
250ml sourcream
2 eggs, beaten
1 tsp vanilla extract
300g (approx) frozen rasberries, defrosted

The recipe says to make 2 23cm cakes, and stick together with rasberry jam; I made one, in a bundt tin, it just needed longer to cook...

Oven to 180C
Melt the chocolate (eg in a bowl over boiling water), let cool slightly
sieve flour and baking soda into a large mixing bowl, add salt and sugar, then stir in the oil and sour cream.
Mix in the melted chocolate. Add in the beaten eggs, vanilla, and 60ml of hot water.
Finally, stir through the rasberries.
Pour into oiled tin (or tins), bake 25 mins (more if single cake). Wait till the cake is fully cooled before remoiving from the tins.

Serve with something like cream!