Preheat your oven to 350°F (175°C) and grease a 9-inch round cake pan with butter. Line the bottom with parchment paper.

Melt ½ cup of unsalted butter, ¾ cup of light brown sugar, and 2 tablespoons of maple syrup in a saucepan over medium heat until bubbly and smooth. Pour into the prepared cake pan and arrange 1 cup of pecan halves on top.

In a large mixing bowl, whisk together 1½ cups of all-purpose flour, 1½ teaspoons of baking powder, ¼ teaspoon of baking soda, and ¼ teaspoon of salt. Set aside.

In a separate bowl, beat ½ cup plus 4 tablespoons of softened unsalted butter and ¾ cup of granulated sugar using an electric mixer until light and fluffy. Incorporate 2 large eggs one at a time and blend in 1 teaspoon of pure vanilla extract.

Gradually add the dry ingredients to the butter mixture, alternating with ½ cup of sour cream and ¼ cup of milk. Mix on low speed until just incorporated.

Pour the batter over the pecan layer in the cake pan, smoothing it evenly.

Bake for 35-40 minutes until a toothpick inserted in the center comes out clean. Watch closely to prevent overbaking.

Let the cake rest in the pan for 10 minutes before inverting onto a serving plate and removing the parchment paper.