Preheat the oven to 180°C/160°C Fan/Gas Mark 4. Grease and line a 8” square tin. Slice the rhubarb into 2 cm wide pieces and place in a bowl. Sprinkle over 50g caster sugar and 1tbsp flour and stir through the rhubarb, set aside.

Place the butter, light brown sugar and Vanilla Paste in a large bowl and beat together until creamed, the sugar should all be mixed into the butter. 

Add the flour and mix together to create a crumble mixture – this can be done by hand or in a mixer.

Once the mixture is crumbly set aside. 

Place the butter and caster sugar into a bowl and cream together until smooth. Add the eggs and Vanilla Paste and beat together until all the egg is combined – if the mixture begins to curdle add a spoonful of flour.

Sieve the flour, Baking Powder and ground almonds over the mixture and fold through until just combined.

Pour the sponge mixture in the prepared tin and smooth to evenly cover the base. Spread the rhubarb on top to create an even layer of rhubarb. Finally Sprinkle the crumble topping over the rhubarb ensuring it is completely covered.

Place the rhubarb crumble cake into the oven and bake for 60 minutes, the crumble topping should be golden brown. 

The crumble cake is best served warm with ice cream or custard.