There's no denying that upside downers give you soggy bottoms, and this tends to be in the extreme when it comes to the plum versions, but I quite like a juicy, syrupy cake so this is just to my liking.
I love the flavour and richness that baking with olive oil gives so I tend to swap it for butter at every opportunity - it works really well in this context along with the savoury nuttiness of the walnuts and rye flour. If you've never baked with oil, I'd definitely give it a go and see what you think.
2 tbsp demerara sugar
10 Victoria plums, stoned, halved and cut into wedges
300ml olive oil
4 eggs beaten with 2 tbsp milk
200g soft brown sugar
150g freshly ground walnuts
150g rye flour
1 heaped tsp baking powder
½ tsp salt
Preheat the oven to 180C/350F/gas 4. Grease and lightly flour a 23cm diameter cake tin. If it's loose-bottomed, wrap the underside tightly in foil. Sprinkle the base of the tin with the demerara sugar, then arrange the plums in concentric circles until the base is completely covered. Put to one side.
With an electric whisk, beat together the oil and the beaten eggs, then whisk in the sugar until there are no lumps. Fold in the walnuts, rye flour, baking powder and salt and rye flour and mix well.
Pour over the plums, then sit on a baking tray and place in the oven for 60-70 minutes until an inserted skewer comes out clean. Depending on the juiciness of your plums, you may find it ends up in the oven for a bit longer even. You may want to protect the top from burning with a little baking paper after 45 minutes or so.
Rest the cake in the tin for 20 minutes before running a knife around the edge to loosen it. Place a large plate on top and carefully invert onto the plate. Remove the tin and replace any dislodged pieces of fruit. Leave to cool before eating.