Not quite what I expected

We've a good crop of rhubarb coming in the garden so for Zac's tonight I'd decided I'd try a new rhubarb cake. It didn't turn out quite as I anticipated ...It's a sponge base topped with rhubarb and covered in a crumble-type mixture. I expected the topping to stay more crumbly but maybe I put too much baking powder in my adapted version of the sponge. Making a larger cake than the recipe is intended for has its own difficulties. Doubling quantities is easy but adjusting temperature and timing is more complicated that you'd think.

It tastes nice though.