Set your oven to 350°F (175°C). Grease a 9-inch round cake pan with butter or non-stick spray.
In a small saucepan over medium heat, melt the butter, brown sugar, and corn syrup together. Stir until smooth and bubbling (about 2–3 minutes). Remove from heat and stir in chopped pecans and a pinch of salt.
Pour the pecan mixture into the bottom of the greased cake pan. Spread evenly using a spatula.In a medium bowl, whisk together flour, baking powder, baking soda, cinnamon, and salt. Set aside.
In a large bowl, whisk together the oil, water, sour cream, eggs, vanilla extract, granulated sugar, and brown sugar until smooth. Gradually add the dry ingredients into the wet ingredients. Stir just until no flour remains. Do not over mix.
Carefully pour the cake batter over the pecan topping in the pan. Smooth the top with a spatula. Place the cake in the preheated oven and bake for 40–45 minutes, or until a toothpick inserted in the center comes out clean.
Remove the cake from the oven and let it cool in the pan for 10 minutes. Run a knife around the edge of the cake to loosen it.
Place a serving plate over the cake pan and carefully invert to release the cake. Let cool slightly before slicing and serving warm or at room temperature.