Preheat your oven to 350°F (175°C). Grease and flour a 9x5-inch loaf pan or line it with parchment paper for easy removal.
In a mixing bowl, whisk together the flour, baking powder, baking soda, salt, cinnamon, and nutmeg. Set aside.
In a large mixing bowl, cream together the softened butter, granulated sugar, and brown sugar until light and fluffy. This should take about 3-4 minutes using an electric mixer.
Add the eggs one at a time, mixing well after each addition. Stir in the vanilla extract.
Gradually add the dry flour mixture to the butter mixture, alternating with the apple cider, starting and ending with the flour mixture. Mix until just combined.
Gently fold in the diced apples and walnuts (if using) until evenly distributed in the batter.
Pour the batter into the prepared loaf pan, smoothing the top with a spatula.
Bake in the preheated oven for 55-65 minutes, or until a toothpick inserted into the center comes out clean.
Once done, remove the cake from the oven and allow it to cool in the pan for 10-15 minutes before transferring it to a wire rack to cool completely.
Notes
Dust the top with powdered sugar and serve with a dollop of whipped cream or a scoop of vanilla ice cream for a delightful indulgence.