1. Preheat a barbecue (or oven) to 190 degrees Celsius (fan, if using an oven), or equivalent. Grease and line a 20cm cake tin with a sheet of greaseproof or parchment paper cut to size.

2. Place the 60g butter and 60g demerara sugar in the lined tin. Transfer to the barbecue over indirect heat (or oven) and allow the butter to melt. Once melted, stir in the sugar so it is evenly distributed around the base of the tin and continue cooking for 10 minutes to caramelise the mixture.

3. Remove the tin from the heat and place the halved plums cut side facing down over the sauce on the base of the tin, leaving as few gaps as possible.

4. With an electric whisk, cream the butter and sugar together until light and fluffy. Add the eggs and vanilla extract. Sieve the flour then fold it through the mixture to give a smooth batter (add a tablespoon of milk to loosen the batter, if it is very stiff).

5. Spoon the batter over the plums, spreading the mixture evenly.

6. Return the cake to the barbecue (or a preheated oven) and bake for 50 minutes. For best results the top should have a dark golden colour (ensuring a nice crunchy caramelised base). Leave to sit in the tin for five minutes before inverting the cake.

7. To remove the cake from the tin, place a plate over the top of the tin and invert the cake so the plums are on the top. Remove the tin and peel away the paper lining.

8. Serve the cake warm with freshly whipped cream or ice cream.

Variation
You can make this with tinned pineapple or pear in the same way. A sprinkle of nutmeg, mixed spice or cinnamon can be added to suite your taste.