Preheat the oven to 350℉/176℃. Line an 8 or 9 inch cake pan with a circular piece of parchment paper along the bottom, and grease the sides. Set aside.
In a bowl, add the dry ingredients; flour, baking soda, baking powder, cornstarch, cinnamon, and salt. Stir to combine and set aside.
1 3/4 cups all-purpose flour, 2 tsp cornstarch, 3/4 tsp baking soda, 3/4 tsp baking powder, 1/2 tsp cinnamon, 1/4 tsp salt
In a large bowl, add the butter, oil, white sugar, eggs, vanilla, sour cream. Whisk together for 2-3 minutes.
1/4 cup unsalted butter, 1/3 cup oil, 2 large eggs, 3/4 cups white sugar, 3/4 cups sour cream, 1 tbsp vanilla
Add the dry and wet ingredients together and with a spatula, gently stir to form a cake batter.
In the cake pan, add melted butter and spread as evenly along the bottom as possible. Then sprinkle brown sugar and chopped pecans.
1/3 cup unsalted butter, 1/4 cup brown sugar, 1 1/2 cups pecans
Take the cake batter and gently spread it on top, making sure not to disturb the layer of pecans. I like to use a cookie scooper for this as I find it's effective and not messy. Spread evenly.
Bake for 45-50 minutes or until the cake come out clean with a toothpick inserted in the middle.
Allow to cool, then gently run a butterknife around the cake pan. Flip the cake upside down onto a flat surface like a plate or a cake stand. Peel the parchment paper off to reveal the gorgeous pecan layer! Then slice, and enjoy!