Mix brown sugar with pepper to create a rub mixture. Using your hands, massage the rub onto both sides of the slices of ham. Ham slices should be completely covered (front and back) with brown sugar mix.
Place ham slices on sheet of lightly greased foil, then place onto grill.
On separate sheet of greased foil, lay pineapple slices out, uncovered. Cook for 6-8 minutes or until brown caramelization appears around edges of ham and pineapple.
Remove ham and pineapple from heat and assemble onto toasted sourdough bread.