In a small saucepan over medium heat, bring the 2 cups of fresh apple cider to a gentle, steady boil. Simmer for 15 to 20 minutes until the liquid reduces down to exactly 3/4 cup of concentrated, amber cider syrup. Remove from heat and cool completely to room temperature.

Preheat oven to 350°F (175°C). Generously grease a 10 to 12-cup metal fluted bundt pan with softened butter, ensuring every ridge and the center tube are thoroughly coated, then lightly dust with flour (tapping out any excess).

In a large mixing bowl, whisk together the sifted all-purpose flour, ground cinnamon, nutmeg, allspice, ginger, baking powder, baking soda, and fine sea salt until well aerated.

In a stand mixer fitted with the paddle attachment, beat the softened butter, brown sugar, and granulated sugar on medium-high speed for 3 to 4 minutes until pale, fluffy, and creamy.

Add the eggs one at a time, beating well after each addition, then blend in the vanilla bean extract.

Whisk the cooled reduced apple cider into the room-temperature buttermilk. With the mixer on low speed, add the dry ingredients in three additions alternating with the cider-buttermilk liquid, beginning and ending with the flour mixture. Mix just until combined and silky; do not overmix.

Pour the thick spiced batter into the prepared bundt pan, smoothing the surface with a spatula.

Bake at 350°F (175°C) for 50 to 55 minutes, until a long wooden skewer or cake tester inserted deep into the center comes out clean with a few moist crumbs.

Let the bundt cake cool in the pan on a wire rack for exactly 10 minutes. Gently invert the warm cake onto the cooling rack.

While the cake is still warm, generously brush all sides with the melted butter, then shower with the cinnamon sugar mixture so it adheres to every fluted ridge like a freshly fried cider doughnut.

Just before serving, slowly drizzle the warm salted caramel sauce over the top, letting it drip into the flutes, and finish with a sprinkle of flaky sea salt. Slice into 12 generous portions!