Position a rack in the center of your oven and preheat the oven to 350°F. Butter or coat a 9-inch round baking pan with nonstick spray. Line the bottom of the pan with a round of parchment paper.

In a large bowl, whisk the brown sugar and eggs until pale and foamy, about 1 minute. Add the oil, vanilla, cinnamon, nutmeg, salt, and whiskey and espresso powder, if using. Whisk until smooth and emulsified.

Add the flour, baking powder, and baking soda and whisk until well-combined and smooth.

Use a rubber spatula to fold in the apples and 1/4 cup of the nuts.

Pour the batter into the prepared pan and use an offset spatula to gently smooth the top, making sure the apples are well dispersed and go all the way to the edges of the pan. Tap the pan gently on the counter to release any air bubbles. Sprinkle the remaining 1/4 cup nuts over the cake.

Bake until puffed and golden, and a tester inserted into the center comes out clean, 30 to 40 minutes. There may be a bit of moisture on the tester from the apples. Set the pan on a rack to cool for about 15 minutes. Run a thin knife around the edge and carefully turn the cake out onto a cooling rack. Then invert it again so that it's puffy side up, if desired.

Store the cake, wrapped tightly or in an airtight container, at room temperature or in the refrigerator for up to two days.