Preheat the oven to 350 F (177 C). Generously grease a 9.5 or 10- inch (10-12 cup capacity bundt pan).
In a large bowl whisk the melted butter, honey, light brown sugar, cinnamon and salt together until well combined. Stir in the chopped pecans. Set aside.
In another bowl whisk the flour, baking powder and salt together until well combined.
In a mixing bowl, beat the butter and oil on medium until smooth and well combined.
With the mixer on low, slowly pour the granulated and light brown sugars into the butter and oil mixture. Increase the speed to medium for about 3 minutes or until the butter and sugar are fluffy and light in color. On the lowest speed, mix in the eggs, sour cream and vanilla extract one at a time. Wait for each ingredient to be fully incorporated before adding the next. The mixture may look slightly curdled. Don’t worry, this is exactly how it should look at this stage.
By hand or on the lowest setting of your mixer, mix in the dry ingredients to the wet, alternating with the buttermilk. This will be done in three rounds- dry, buttermilk, dry, buttermilk, dry. If you are familiar with vanilla pound cake, this cake batter will look very similar.
Evenly pour the pecan pie topping into the prepared bundt cake pan. If the topping has started to solidify, heat the microwave safe bowl for about 20 seconds. Top the pecan pie filling with the vanilla cake. Evenly spread the cake around the bundt pan.
Bake the upside down pecan cake for about 30 - 40 minutes. The edges of the cake will pull slightly from the sides of the pan. The cake will bounce back quickly when gently pressed into the center of the cake. Remove the bundt cake from the oven to cool on a cooling rack for about 10 minutes.
To remove: Place a serving plate or even another cooling rack on top of the bundt pan. Invert the pan so the top of the bundt cake is now on the bottom (on the serving plate or second cooling rack). Gently tap all around the pan to help loosen any pieces of cake that may be stuck. Gently lift up the pan. If some pieces of pecan filling remain stuck to the pan, simply scoop them out and top the cake. Allow the cake to cool to room temperature before enjoying.