Preheat the oven to 350 F (177 C). Generously grease a 10 inch (12 cup capacity bundt pan) or a 9 -10 inch (23 cm) cake pan.
In a large mixing bowl whisk the flour, baking powder and salt together until well combined.
2¼ cups (270 g) all purpose flour , 1½ teaspoon baking powder, ½ teaspoon salt
Using a stand mixer fitted with a whisk attachment cream the room temperature butter and oil on medium until smooth and well combined. Decrease the mixer to low speed, slowly pour the granulated and light brown sugars into the butter and oil mixture. Once all the sugar has been added, increase the speed to medium for about 3 minutes or until the butter and sugar are fluffy and light in color.
¾ cup (170 g g) unsalted butter, room temperature, 3 tablespoons (45 ml) canola oil , ¾ cup (150 g) granulated sugar, ¾ cup (150 g) light brown sugar
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 a little curdled at this point. Don’t worry, this is exactly how it should look at this stage.
3 large eggs (US), room temperature, 1 tablespoon (60 ml) vanilla extract , ⅓ cup (90 g) sour cream, room temperature
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. Set aside for a minute to make the pecan pie filling topping.
¾ cup (180 ml) buttermilk, room temperature
In a large bowl whisk the melted butter, honey, light brown sugar, cornstarch, cinnamon and salt together until well combined. Stir in the chopped pecans. Evenly pour the pecan pie topping into the prepared cake pan. Top the pecan pie filling with the vanilla cake. Evenly spread the cake around the pan. ½ cup (100 g) light brown sugar, ½ cup (118 ml) melted butter, ¼ cup (59 ml) honey , ¾ teaspoon cornstarch, ½ teaspoon ground cinnamon , ¼ teaspoon salt , 1½ cups (95 g) pecans, chopped
Bake the upside down pecan cake for about 45 - 60 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 cake from the oven to cool on a cooling rack for about 8 - 10 minutes.
To remove the cake from the pan, place a serving plate or even another cooling rack on top of the cake pan. Invert the pan so the top of the 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 while the cake is still hot. Allow the cake to cool to room temperature before enjoying.