We have one lone rhubarb plant in the garden, and there was just enough ready to pick to use in this cake.
I've adapted the recipe to the kind of cake I wanted, so I'm claiming it as mine now! It makes a small amount of rhubarb into a delicious dessert, tho' it's not a big cake if you have a family to feed.
150g caster sugar
90g plain flour
1/2 tspn baking powder
about 250g rhubarb
50g cold butter
1 tspn cinnamon
2 tbspn pearl sugar
Preheat oven 175C/gas 3/4
Grease and line a 20cm springform tin [make sure you grease the tin well or the cake will stick like glue!]
Cut the rhubarb into about 1cm pieces.
Beat the eggs and sugar with a mixer till it's pale and nice and fluffy. Then fold in the flour and baking powder.
Pour this batter into the tin and put the rhubarb on top, pushing it into the batter.
Then cut the butter into thin slices - it needs to be very cold [straight from the freezer cold as suggested by Phil] and very quickly becomes difficult to slice. I used a potato peeler then changed to a small sharp knife. Put the butter on top of the batter and sprinkle the pearl sugar over.
The pearl sugar disappeared with the butter, and gives a lovely crunchy layer on top of the cake, and the rhubarb was moist underneath. I sprinkled a bit of icing sugar on top.