Preheat oven to 350°F. Grease and flour 12-cup bundt pan. Tap out excess flour. Set aside.
In a large bowl, whisk together flour, cinnamon, baking soda, baking powder, and salt. Set aside.
In the bowl of a stand mixer fitted with a paddle attachment (or using a hand mixer), mix together butter, brown sugar, and sugar. Add eggs and mix until combined.
Add about 1/3 of dry flour mixture. Mix on low speed. Add rum and half of persimmon puree. Mix and add another 1/3 of flour mixture. Add remaining puree. Toss dried dates in remaining flour. Add flour and dates to batter. Stir together until there are no longer and dry streaks of flour.
Add walnuts and fold until thoroughly distributed.
Pour batter into prepared bundt pan. Bake for 55-60 minutes until toothpick inserted in center of cake comes out clean. Let cake cool in pan for 10-15 minutes. Invert cake onto a wire rack and cool to room temperature.