Preheat oven to 350 degrees. Grease a loaf pan, set aside.
Mix cinnamon & sugar mix together in small bowl and set aside.
Cream butter & sugars together (by hand or with mixer), add in egg. Add baking powder, baking soda, half the flour & mix well. Mix in sour cream & vanilla. Add the remaining flour & mix well.
Pour ½ the batter into prepared loaf pan. Sprinkle with cinnamon & sugar mix, then cover with the second ½ of the batter.
Bake for 45-55 minutes, or until toothpick inserted in center comes out clean.
Let cool in pan for 15 min. then transfer to cooling rack or plate, slice when completely cooled.
Recipe by THE SEMISWEET SISTERS at https://www.thesemisweetsisters.com/2018/04/30/cinnamon-swirl-sour-cream-pound-cake/