Slice up the apples. You could leave the skin on if you like. As I was intending to cook the sponge in the microwave, and it only takes 6 minutes, I thought there was a risk of the apples not being cooked enough, so I gave them a blast for a couple of minutes first to soften them. No sugar, apples really don't need it
Now mix the sugar and vegetable oil in a bowl, with a wooden spoon, and beat in 1 egg. I just put the whole egg in at once, it doesn’t seem to curdle when using oil and gave it a good beat until it all comes together. It wouldn’t matter if it did curdle by the way, just bung the flour in anyway, it will be fine.
Then stir in the self raising flour and when well mixed, spread it on top of the cooled apples.
Then into the microwave on High (1000w) for 6 minutes.
When cooking sponges in this way, the top of the sponge will feel a little sticky, and may seem to be not cooked enough, but don’t be tempted to give it another minute or two, or the sponge will be dry and maybe a bit tough as well. As you can see, it looks pasty and not particularly appetising when cooked in a microwave instead of the oven. But 6 minutes in a microwave costs almost nothing in fuel, and the sponge only gets covered in custard or ice cream, so it doesn’t notice once it is served.