01 -
Heat your oven to 350°F and position a rack in the center. Generously butter a 9-inch round cake pan, then line the bottom with parchment paper for easy removal later.
02 -
In a large mixing bowl, vigorously whisk together the brown sugar and eggs until the mixture becomes pale and slightly foamy - this takes about a minute of good whisking. Stir in the oil, vanilla, warm spices, salt, and the optional whiskey and espresso powder until everything is beautifully smooth and well combined.
03 -
Gently whisk in the flour, baking powder, and baking soda until you have a smooth, lump-free batter. Don't overmix - just until everything comes together nicely.
04 -
Using a rubber spatula, carefully fold in all the diced apples and about ¼ cup of the chopped walnuts, making sure they're evenly distributed throughout the batter.
05 -
Pour the batter into your prepared pan and use an offset spatula to spread it evenly, ensuring the apple pieces reach all the way to the edges. Give the pan a gentle tap on the counter to release any air bubbles, then sprinkle the remaining ¼ cup of nuts over the top. Bake for 30-40 minutes until the cake is golden brown and puffed, and a toothpick inserted in the center comes out mostly clean (a little apple moisture is fine).
06 -
Let the cake cool in the pan for about 15 minutes, then run a thin knife around the edges and carefully turn it out onto a cooling rack. Flip it right-side up if you like. The cake stays fresh wrapped tightly at room temperature or in the fridge for up to two days.