In a small bowl mix the salt, chile powder, and brown sugar. Sprinkle over both sides of the pineapple slices. Place pineapple slices onto a preheated, oiled grill or grill pan on high heat for 1 minute on each side. Reduce heat to low and continue cooking for 2 to 3 minutes per side or until the pineapple has softened and the sugar has caramelized on the edges.