Grease a 10" round cake pan with oil. Line the sides and the bottom of the pan with parchment paper, and grease the paper. Set it aside.

In a medium saucepan, mix the butter, maple syrup, brown sugar, corn syrup if using, and salt.

Bring the mixture to a boil over medium heat, and let it simmer for about 3 minutes. Add the vanilla and mix to combine.

Remove the caramel from the heat and pour on the bottom of the prepared pan.

Scatter the chopped pecans on top of the caramel on an even layer. Set it aside.

Pre-heat the oven to 350ºF.

In a bowl mix together the flour, baking powder, baking soda, salt, cinnamon, and nutmeg. Whisk to combine and set aside.

In a large mixing bowl or in the bowl of a stand mixer, beat the butter for one minute. Add the granulated and brown sugar, and beat on medium-high speed for 2 more minutes.

Add the eggs, one at a time, stirring until completely incorporated before adding the next egg. Also make sure to scrape the sides and the bottom of the bowl in between additions.

Add the vanilla and stir to combine.

Add half of the flour mixture to the bowl and stir on low.

Pour the buttermilk in and stir.

Add the remaining dry ingredient mixture and stir until incorporated.

Once the batter is smooth, add the pecans and fold gently until combined.

Pour the batter over the pecan caramel topping on the bottom of the pan. Spread with a spatula until smooth.

Bake the cake in the oven for about 40 to 50 minutes, or until a toothpick comes out clean when inserted in the cake.

Let the cake cool down for about 15 minutes, then flip it upside down onto a plate.

Allow for it to cool down completely before slicing and serving.