In a small bowl, combine the sugar, onion powder, cinnamon, nutmeg, ginger, cloves, and paprika. Mix well.
Cover a baking sheet with aluminum foil, and place the ham sliced side down onto the foil. If you do not use aluminum foil, you may have burnt sugar on your pan, and it will take a while to clean off.
Sprinkle the outside of the ham with the seasoned sugar, pressing the sugar onto the ham. You might not use all of the sugar.
With a blowtorch, gently heat the seasoned sugar on the ham. Wave the flame quickly over the sugar - you want it to brown, not burn. Staying in one area, and slowly moving out from there will make this easier, as you will be heating the sugar in a continual direction. This process will take about 15 minutes, so be patient. If you prefer a thicker crust, you can sprinkle more sugar on top of the already browned parts of the ham. Be sure to brown the newly added sugar.
When you are happy with the crust, you can either reheat the ham or serve it cold.