In all honesty, the origin of this cake is simply that I cannot make a go of a lemon meringue pie. I've tried, and I've tried, and it's not that I've utterly failed, but I haven't completely delighted myself. There's enough of that kind of falling short in the rest of life, without having to usher in disappointment and self-loathing in the kitchen. This, then, is the easy option. And the funny thing is, the layers of sponge, with their crisp-carapaced squashy-bellied meringue topping are…