Prepare the barbecue 30 minutes before you want to eat. (Alternatively, preheat the grill to its highest setting.) Soak 5-7 wooden skewers in cold water for 30 minutes, then shake off any excess moisture and set aside.
Heat the sugar and water in a saucepan over a low heat, stirring regularly, until the sugar has dissolved.
Add the vanilla pod, vanilla seeds and lime zest to the pan and bring the mixture to a simmer. Continue to simmer for 10-12 minutes, or until the mixture has thickened to a syrup.
Add the rum, if using, and stir to combine.
Push one piece of pineapple onto each prepared skewer.
When the flames of the barbecue have died down and the coals are ash-white, place the pineapple skewers onto the grill and cook for 8-10 minutes, turning regularly, or until pale golden-brown on all sides and softened. (NB: If cooking the pineapple skewers under the grill, place them onto a baking tray lined with aluminium foil before cooking.)
To serve, place one grilled pineapple skewer onto each of eight serving plates. Drizzle over the lime, vanilla and rum syrup. Serve a scoop of ice cream alongside, if using.
Type the ingredients you want to use, then click Go. For better results you can use quotation marks around phrases (e.g. "chicken breast"). Alternatively you can search by chef, programme, cuisine, diet, or dish (e.g. Lasagne).