Preheat the oven to 190°C (Gas Mark 5 / 375°F).
Add the sliced pears to a large saucepan, along with the cinnamon and nutmeg. Cook over a medium-low heat for 5-10 minutes, stirring occasionally, until soft (add a small dash of water if the pears seem to be sticking).
Meanwhile, add the diced butter and self-raising flour to a large bowl, and rub together using your fingertips until the mixture resembles breadcrumbs. Add the sugar and egg, and mix thoroughly with a fork until well combined (but still breadcrumb-like).
Grease an 8-inch loose-bottomed springform cake tin with butter, and add about two thirds of the cake mixture. Press the mixture into the base of the tin, allowing it to rise up the sides just a little.
When the pears are soft and any excess liquid has cooked off, transfer them into the cake tin on top of the base. Spread them out into an even layer, and drizzle generously with caramel sauce. Sprinkle the remaining cake mix on top (you don't need to press it down at all).
Bake for around 30-35 minutes, until golden brown. Serve warm or cold.