Step 1

Heat the oven to 180C/fan 160C/gas 4 and line a 900g loaf tin with a long strip of baking paper. For the cake, tip the butter, sugar and treacle into a large bowl and use an electric whisk to beat until really light and fluffy. Crack in the eggs and whisk to combine – don’t worry if it splits as it will all come together. Add the flour, bicarb, ground ginger, stem ginger, rum and ½ tsp of fine sea salt, and fold together until evenly combined. Scrape into the tin and bake for 40 minutes or until a skewer poked into the centre comes out clean. Cool in the tin for 10 minutes before transferring to a wire rack to cool completely. If making ahead, wrap really well in baking paper and set aside at room temperature.

Step 2

To make the rum caramel, evenly sprinkle the sugar into a non-stick frying pan and put over a medium heat. Cook until the sugar is fully melted, then turn up the heat and cook, swirling the pan, until the caramel is a deep amber colour. Carefully add the butter, then pour in the cream and gently bubble the mixture until thickened. Pour in the rum and remove from the heat. Cut the pineapple into quarters lengthways, remove the core, then cut each piece in half lengthways again.

Step 3

Cut the cake into 4cm-thick slices and heat a barbecue to medium (after you’ve cooked your main meal and the coals are dying down is the perfect heat). Give the bars a good wipe with half of a lemon if you’ve been cooking meat beforehand. Put the pineapple slices on the grill and cook for 1-2 minutes, basting with the caramel sauce until charred, caramelised and softening but still with a little bite. Put the cake slices on the grill and cook for a minute on each side until just toasted, then baste with a little of the caramel sauce. Alternatively, if you’re cooking indoors, grill the cake under a hot grill for 1 minute on each side (keep an eye on it or it may catch) and pan-fry the pineapple in a dry, non-stick frying pan for 3-4 minutes on each side until charred, finishing with a few spoonfuls of sauce to glaze.

Step 4

Serve the cake slices with the charred pineapple, left-over rum caramel sauce and scoops of vanilla ice cream.