Preheat your oven to 350°F (175°C).

Grease your 9x13-inch sheet pan with butter or non-stick spray and set aside.

Peel and dice your apples into small, even pieces (about ½-inch cubes). This ensures they bake evenly throughout the cake.

In a medium bowl, whisk together the all-purpose flour, baking powder, baking soda, ground cinnamon, ground nutmeg, and salt.

Whisking well helps distribute the spices and leavening agents evenly for a balanced flavor and proper rise.

In a large bowl, use an electric mixer or hand whisk to cream the softened butter, granulated sugar, and brown sugar until light and fluffy. This usually takes about 3-4 minutes on medium speed.

Pro tip: Scrape down the sides of the bowl occasionally to ensure everything gets mixed evenly.

Crack in the eggs one at a time, mixing well after each addition so they fully incorporate.

Stir in the vanilla extract until combined.

Alternately add the dry ingredients and buttermilk to the butter mixture, beginning and ending with the dry ingredients.

Mix gently after each addition just until combined—avoid overmixing, or your cake might turn out dense.

Pro tip: Use a spatula to fold in the last bits of flour to keep the batter light and airy.

Gently fold the diced apples into the batter using a spatula, ensuring they’re evenly distributed.

Be careful not to overmix here to avoid bruising the apples and turning the batter too dense.

Pour the batter evenly into the prepared sheet pan and smooth the top with a spatula.

Bake for 35-40 minutes, or until a toothpick inserted in the center comes out clean or with just a few moist crumbs.

Pro tip: Start checking at 30 minutes to avoid overbaking, as oven temperatures can vary.

Allow the cake to cool completely on a wire rack before glazing. This helps the glaze set properly and prevents it from melting into the cake.

To make the glaze, whisk powdered sugar, milk, and vanilla together in a small bowl until smooth.

Drizzle the glaze evenly over the cooled cake.

Slice into squares and serve as is, or add a scoop of vanilla ice cream or a dollop of whipped cream for an extra special treat.