For the Brown Sugar/Pecan Filling:
1/3 cup firmly packed light-brown sugar
2 teaspoons ground cinnamon
2 teaspoons all-purpose flour
1 cup coarsely chopped pecans
For the Cake:
Vegetable-oil cooking spray
3 1/2 cups all-purpose flour, plus more for pan
2 teaspoons baking powder
1/2 teaspoon baking soda
1/2 teaspoon salt
10 tablespoons (1 1/4 sticks) unsalted butter, room temperature
1 cup sugar
3 large eggs
1 3/4 cups sour cream
Prepare the filling: In a small bowl, combine brown sugar, cinnamon, flour, and pecans; set aside.
Prepare the cake: Preheat the oven to 350 degrees. Spray a 10-inch nonstick Bundt pan with cooking spray; set aside.
Into a medium bowl, sift together flour, baking powder, baking soda, and salt; set aside. In the bowl of an electric mixer fitted with the paddle attachment, cream butter and sugar until light and fluffy, starting on low speed, then increasing speed to medium. Add eggs, one at a time, beating well after each addition and scraping down sides of the bowl.
While beating on low speed, add the flour mixture, alternating with sour cream, and beginning and ending with the flour mixture. Beat just until well combined, scraping down sides several times.
Spoon half the batter into the prepared pan. Sprinkle evenly with the reserved filling. Top with remaining batter.
Bake until golden brown and a toothpick inserted in the center comes out clean, 50 to 60 minutes. Let cake cool in the pan for 10 to 15 minutes, then turn the cake out onto a rack to cool completely. Dust with confectioners’ sugar.