Simply cook the pork on the stove over a medium heat.
Light the barbecue. Put all the spice mix ingredients in a mortar or blender and grind well. Chargrill the peppers on the barbie until black. When cool enough to handle, peel, seed, cut into finger-length strips and set aside.
Dip the pork in the melted butter, then roll it in the spice mixture until well covered. Heat a heavy frying pan or griddle pan on the barbecue. Drizzle a little melted butter into the pan and fry the meat for 10 minutes, turning occasionally until slightly blackened.
Remove the pork from the pan, wipe the pan with kitchen paper then return the pork to it. Drizzle over a little more melted butter, throw in the peppers and tomato sauce and pour over the beer. Simmer for 15-20 minutes, stirring occasionally, until the sauce is thick and coating the pork.
Using tongs, remove the pork from the pan. Cut it into slices and arrange on a serving plate. Stir the sugar into the sauce and pour it over the pork. Scatter over the celery leaves or rocket, and serve.