Preheat the oven to 325°F. Generously grease a 9-inch square pan; set aside.
Combine the sugar, pecans, and cinnamon in a small bowl; set aside.
Beat the butter and sugar until light and fluffy.
Beat in the eggs, one at a time, mixing well after each addition. Beat in the sour cream and vanilla until combined. The batter may look curdled at the point, this is okay.
Sift the flour, baking powder, baking soda, and salt. Add it to the butter mixture and mix just until fully combined. Take care not to over mix.
Using a small offset spatula, spread half the batter evenly into the bottom of the prepared pan.
Sprinkle ⅔ of the filling mixture over the batter. Top with the remaining batter followed by the remaining filling.
Bake for 50 minutes or until a toothpick inserted into the center comes out clean.
Cool on a wire rack for 10 minutes then remove the cake from the pan and cool completely.
