Preheat oven to 350°F and adjust the oven rack to middle-low position. Spray the baking pans and then layer with parchment paper.
In a large bowl, whisk the flour, salt, and baking powder together. Set aside.
3 cups all-purpose flour, ½ tsp kosher salt , ½ tsp baking powder
In a large measuring cup, stir the buttermilk, vanilla extract, and almond extract together.
1 cup buttermilk, 2 tsp pure vanilla extract, 1 tsp almond extract
In the bowl of a stand mixer fitted with the paddle attachment, cream the butter and shortening together for 2 minutes.
1 cup unsalted butter, ½ cup vegetable shortening
Add the sugar, ¼ cup at a time, and beat until pale, yellow, creamy, and somewhat fluffy, about 3 minutes.
3 cups granulated sugar
Add the eggs, one-at-a-time, beating until well combined after each addition.
5 large eggs
Add the flour mixture to the butter mixture, alternately, with the buttermilk mixture. Start and end with the flour mixture. Mix just until no dry flour can be seen but don’t over-mix. Set aside while you make the filling.
To make the filling: In a medium saucepan, whisk the eggs until foamy. Add the granulated and brown sugars, salt, and melted butter, and whisk until well combined. Set the saucepan over medium-low heat, stirring often until the mixture is hot to the touch, but not boiling. Add the lemon juice and half of the chopped pecans and stir well.
3 large eggs, ½ cup granulated sugar, ¼ cup dark brown sugar, ⅛ tsp kosher salt, 3 tbsp unsalted butter, ½ lemon, 2 cups toasted rough-chopped pecans
Fill each pan with half the batter, sprinkle each with the remaining pecans, and then pour about ½ of the pie filling over the pecans in each pan. Do not swirl the pie filling into the batter.
Bake cakes at 350°F, set side-by-side, for 1-1½ hours. Turn the pans around after an hour and cover very loosely with foil. (My cakes took about 1½ hours, but start checking the cakes at 70 minutes and check every 5 minutes thereafter). The cakes are done when the internal temperature registers 210°F on an instant-read thermometer, or when a toothpick inserted in the middle of the cakes comes out clean.
Transfer the cakes to a cooling rack to cool for 15 minutes, then lift the cakes out of the pans. Cool the cakes completely before slicing.