Prepare Fruit:

1. Put all of the dried fruit into a large bowl, except chestnuts. 
2. Combine the chestnuts with the apple juice in a medium saucepan and bring to a simmer over high heat.
3. Lower heat to medium and cover with a lid. Simmer for 10 minutes. The chestnuts should be moist and soft.
4. Pour the chestnuts and the hot apple juice over the dried fruit and let sit for 30 minutes. Drain the apple juice from the fruit using a colander and use the juice for another purpose or discard. Set the fruit aside to cool to room temperature.

Prepare the Cake:

1. Heat the oven to 325°F and move the oven shelf to the middle of the oven.
2. Spray a 12-cup bundt pan with baker’s cooking spray, making sure you get all of the nooks and crannies.
3. In a medium bowl, whisk together the flour, baking powder, and salt until well blended. 
4. With an electric mixer (I use the paddle attachment on my stand mixer), beat the butter until it’s very pale and little tails have formed, about 1 minute on medium high speed. 
5. Add in the sugar and beat well until slightly fluffy, about 2 minutes. 
6. Scrape the sides of the bowl well. Add the eggs one at a time, beating until completely blended before adding the next. 
7. With the mixer on the lowest setting, add one-third of the flour and mix until almost combined; then add half the buttermilk and mix until just combined. Repeat with another third of flour, and then the last half of the buttermilk plus the vanilla extract and the orange oil. Add the last third of the flour and mix until almost combined. It’s fine to still have small streaks of unmixed flour.
8. Using a stiff rubber spatula, add all of the fruit and slowly stir to blend it into the flour mixture, taking care to scrape the bowl’s bottom and sides.
9. Scrape the batter into the prepared pan and bake until the cake is golden brown and a toothpick comes out with just a few crumbs clinging to it when inserted in the center, 65-70 minutes. 
10. Let the cake cool for about 10 minutes; flip it out gently onto a cooling rack and cool completely before serving.