Make sauce first. Soak dates in 1 cup water for 15 minutes. Place dates WITH the water in blender and process until smooth. Add date mixture to saucepan and stir in ancho chili powder and salt. Bring to boil for 1 minute and then lower to simmer and continue to simmer, stirring occasionally, until reduced by about 1/2 in volume. Remove from heat and let cool.
Remove seeds from cantaloupe, but leave skin on. Slice into wedges, approximately 1/2″ thick.
In small bowl, toss together 1/2 tsp ancho chili powder, 1/2 tsp salt and 1 tbs. brown sugar. Sprinkle over both sides of cantaloupe.
Heat grill to approximately 400F degrees. Grill cantaloupe for 2 minutes per side, or until grill marks have formed and slightly softened but not completely wilted.
Plate cantaloupe slices and drizzle with date syrup. Sprinkle with crushed pistachios and serve. Leftover date syrup may be stored in fridge for a week and used for other purposes.