Preheat your oven to 350°F (175°C) and grease and flour your bundt pan.
Cream the softened butter, brown sugar, and granulated sugar until light and fluffy.
Beat in the eggs one at a time, then stir in the vanilla extract.
In a separate bowl, whisk together the all-purpose flour, baking powder, and ground cinnamon.
Gradually add the dry ingredients to the wet mixture, alternating with the diced apples.
Pour the batter into the prepared bundt pan and bake for 50-60 minutes.
Allow the cake to cool in the pan for 10 minutes before transferring it to a wire rack.
Optional: In a small bowl, mix ½ cup powdered sugar with 2 tablespoons brown sugar. Add just enough milk (1–2 tsp) to create a smooth, pourable glaze. Drizzle over the cooled cake.