Heat oven to 350 degrees F. Grease a 9 x 5 x 3 inch loaf pan and set aside.
For the Filling and Topping:
For the swirl mixture, in a small bowl combine the cinnamon, sugar and pecans and set aside. Melt 2 tablespoons of butter and set aside to cool.
For the Cake:
In a medium bowl, thoroughly combine flour, baking powder, baking soda, and salt. Set aside.
In large bowl, using an electric mixer, beat the remaining 1/2 cup butter with the sugar until fluffy.
Beat in the vanilla. Add the eggs, one at a time, beating well after each addition.
Beat in the flour mixture one-third at a time, alternating with the sour cream, until well combined.
Pour half the batter into prepared pan and cover with half the cinnamon pecan mixture. Spread remaining batter over and top with remaining cinnamon pecan mixture.
Sprinkle on the reserved melted butter. With a butter knife, swirl mixture into the batter.
Bake 50 to 60 minutes, or until a toothpick inserted in the center comes out clean. Cool in pan on a rack and remove from pan when completely cool.
Notes
When greasing the loaf pan, use the butter wrapper after you take it off the softened butter.
Use a butter knife to swirl the pecan mixture and batter together.