Mine didn't turn out anywhere near as neat though - not having a large enough cake tin as soon as i put mine in the oven and it started to rise it was a cake volcano - oozing all over my oven!
Method: Bung the butter & sugar in the processor and whizz to a thick cream together. Add two eggs, whizz. Add 4tbsps of the flour. Whizz. Ad the last two eggs. Whizz. Add the rest of the flour. Whizz. That’s your cake batter.
Pour it into your well-greased cake tin. Scatter over the chopped rhubarb. (You don’t mix it in as it would all just sink to the bottom. This way it distributes itself pretty evenly through the cake as it cooks.) Mix together the butter and flour in the food processor. Pour the resulting crumbs over the rhubarb, and sprinkle over the sugar. That’s your crumble topping.
Put in the oven for at least 35 mins. It’s cooked when a knife inserted in the middle comes out clean.