Preheat oven to 350F, with rack on lower middle position. Grease a Bundt baking pan and set aside.
In a large bowl, beat butter and sugar until light and fluffy, about 3-5 minutes.
Add eggs one at a time, beating after each addition. Add vanilla and beat to combine.
In a separate bowl, whisk together flour, baking soda, and salt.
Add half of flour mixture to butter/sugar mixture and beat just enough to incorporate. Add half of sour cream to this mixture and beat just enough to incorporate. Repeat for remaining flour mixture and sour cream, beating just to incorporate after each addition. Batter should be smooth.
Make the streusel by combining cinnamon, nuts, and sugar in a bowl.
Transfer a third of the batter into the prepared Bundt pan. Sprinkle a third of the streusel mixture evenly over batter. Repeat layering two more times, ending with streusel on the top.
Bake 60-65 minutes or until toothpick inserted in middle comes out almost clean.