Preheat the oven to 180C/170C fan/gas mark 4. Butter a 23cm springform tin.
Beat 125g butter and 125g caster sugar together until pale and fluffy.
Add 3 lightly beaten large eggs a little at a time, beating well after each addition, then add 2 tsp vanilla extract. If the mixture starts to curdle, add 1 tbsp of the flour.
Fold in the remaining 125g self-raising flour, then add enough milk to give the batter a reluctant dropping consistency. Scrape into the prepared tin.
Toss 675g rhubarb (trimmed and cut into 2.5cm lengths) and 100g raspberries with 5 tbsp caster sugar and spread it over the top of the cake batter.
For the crumble, rub 170g plain flour and 100g cold cubed butter together with your fingers until the mixture resembles breadcrumbs. Stir in 100g golden caster sugar and 100g flaked almonds and scatter this over the fruit.
Bake for 1 hour 20 minutes. The top should be golden and a skewer inserted into the middle of the cake should come out clean.
to cool in the tin, then carefully remove the ring and base. Dust with icing sugar to serve.