Pre heat the oven at 180 deg C and line an 8 inch round baking pan (I used foil).
In a bowl, whisk together the flour and ground almonds and keep aside.
In another bowl, add the white chocolate and vegetable oil and melt together. Keep aside.
In a large bowl, beat together the eggs and caster sugar till pale and frothy.
Tip in the chocolate mixture and fold in.
Fold in the vanilla extract.
Tip in the flour mixture and fold in till everything comes together. Fold in gently and do not over mix. The batter will be quite thick.
Transfer the batter into the lined baking pan and smooth the top.
Arrange the rhubarb pieces on the top in a single layer.
Sprinkle the almond flakes on top.
Place the pan in the centre of the pre heated oven and bake for 35-40 minutes or till a toothpick inserted through the centre of the cake comes out clean (see notes below).
Place the pan on a wire rack for a few minutes. Then remove the foil carefully and cool completely before slicing and serving.
Store any leftovers in an air tight container. But do use it up quickly.