- Preheat oven to 350 degrees and grease a 4×8×12-inch baking pan with 1 tablespoon butter.
- Combine purée with buttermilk.
- Beat stick of butter with sugar in bowl of standing mixer fitted with paddle attachment until fluffy. Add eggs one at a time.
- Turn mixer off and use spatula to fold persimmon mixture into butter by hand.
- Sift dry ingredients together in separate bowl and fold thoroughly into wet ingredients, again by hand.
- Pour mixture into prepared pan. Set this pan into a larger one and fill bottom pan halfway up with hot water. Bake uncovered for at least 1 hour and 15 minutes. You will know it is done when pudding pulls away from sides of pan and is firm in center. A knife blade inserted into center should come out clean.
- Serve hot with fresh whipped cream. This keeps nicely, refrigerated, for 4 or 5 days and reheats well in microwave.