Nigel Slater's moist plum cake

It's a good time of year to benefit from friends and neighbours fruit crops. We were asked to help ourselves to plums from a friends tree this weekend, which I did willingly. Avoiding all the wasps, sleepy and drunk from the over ripe plums, I came away with a lovely bag full. This recipe is from Nigel Slaters Kitchen Diaries, it can be eaten as a cake or warm as a pudding. Clotted cream is an extravagant but very necessary extra. 

Ingredients
150g butter
150g unrefined golden caster sugar
16 plums (size dependent, less if large plums)
3 large eggs
75g plain flour
1 tsp baking powder
100g ground almonds
50g shelled walnuts (I didn't use these)
Method
Set the oven at 175ºC. Line the base of a 20-22cm cake tin with baking parchment.
Beat the butter and sugar until it is pale and fluffy. A food mixer will do this far more efficiently than by hand. Stop when the mixture is light, soft and the colour of vanilla ice cream. Meanwhile, halve the plums, remove the stones, then cut each half in two.
Break the eggs, beat lightly with a fork, then add them bit by bit to the butter and sugar. Sift the flour and baking powder together and fold them gently into the mixture. I do this with a large metal spoon rather than the food mixer. Fold in the ground almonds, then chop the walnuts so they are the size of small gravel, then fold them in, too.
Scrape the mixture into the cake tin. Place the quartered plums on the cake mixture. Bake for 40-45 minutes, then test with a skewer. If it comes out clean, the cake is ready. Remove from the oven and leave to cool for 15 minutes before turning out.