Prepare oven and pan:

Preheat the oven to 350°F. Grease a 9-inch springform pan with baking spray, and line the bottom of the pan with parchment paper.

Combine dry ingredients:

Whisk the flour, baking soda, and kosher salt together in a medium bowl; set aside.

Prepare Cake batter:

Using a stand mixer fitted with the paddle attachment, beat the butter, brown sugar, and sugar together on medium speed for 3 minutes. Add the egg and beat until well combined.

Add wet ingredients:

Add the buttermilk, sour cream, and vanilla to the batter and mix until combined, scraping down the sides and bottom of the bowl as needed to ensure all ingredients are fully mixed together.

Fold in flour mixture:

Add the dry ingredients all at once and, using a rubber spatula, fold into the batter just until combined and there are no more pockets of flour remaining. Be careful not to overmix.

Bake Cake:

Pour the batter into the prepared pan and smooth into an even layer.

Bake in the center of the oven for 30 minutes, until a toothpick inserted in the center comes out clean. When the cake has about 10 minutes left in the oven, prepare the pecan topping.

Prepare Pecan Topping:

Stir the brown sugar, kosher salt, cinnamon, and chopped pecans together in a medium bowl. Add the melted butter and heavy cream and stir to combine.

Add topping and finish baking Cake:

After 30 minutes, remove the cake from the oven and spoon the pecan mixture in dollops over the surface of the cake. Gently spread the pecan mixture into an even layer (the hot cake should warm the pecan mixture, making it more easily spreadable). Return the cake to the oven and bake for an additional 10 minutes.

Cool ready to serve:

Allow the cake to cool in the pan for 20 minutes. Carefully run an offset spatula or butter knife along the edges of the pan to help release any pecan topping that might be sticking before removing the sides of the springform pan. Allow to cool completely before serving.