Preheat the oven to 170°C/fan 160°C/340°F/gas mark 3.
Oil two 23cm cake tins and line the bases with baking parchment.
In a large bowl, sift together the Homepride flour, cocoa powder, baking powder and salt. Stir in the sugar. In another bowl, measure the oil, 400ml water and vanilla extract, and then add to the flour mixture, stirring in the vinegar last of all.
Pour the batter into the prepared tins and bake for 30–35 minutes, or until a skewer emerges clean.
Leave the cakes in the tins for a few minutes, and then run a knife around the rims and turn out on to a wire rack. Remove the baking parchment and leave to cool completely.
Put one cake on a cake stand or serving plate, and top with most of the raspberries. Place the other cake on top, and scatter with the remaining raspberries. Sift over an even layer of icing sugar to serve.
Fiona Cairns has provided this recipe to support Wallace & Gromit's BIG Bake
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