In a medium bowl combine the chopped toasted pecans, brown sugar and cinnamon. Mix well in set aside.
For the Cake
Preheat oven to 325F and coat the inside of your bundt pan with baking spray, or butter and flour it. Sift flour, baking soda and salt in a large bowl then whisk together and set aside.
Cream butter and sugar on high for about 4 minutes or until light and fluffy. Scrape the bowl down halfway through.
Add the eggs one at a time while mixing on medium. Scrape bowl down as needed.
Dump in the flour mixture and mix on low speed until just combined then add the sour cream and vanilla and mix until combined. Scrape down the bowl one last time and mix any stray bits in.
Add half of the batter to your bundt pan then sprinkle the pecan filling over the top and add the remaining batter. Smooth the top with a spatula then bake for about 70 minutes or until a skewer inserted in the middle comes out clean. Allow cake to rest in pan for 5 minutes then invert onto a wire rack and allow to cool completely.
For the Icing
Sift powdered sugar into a large bowl, add the milk and vanilla then whisk until smooth. You can mix in milk a teaspoon at a time if needed to thin the consistency out a bit. Spoon icing over the cooled cake.
Video
Notes
Measure your flour correctly! Adding too much flour to the recipe is the most common mistake. The best, and easiest way to measure flour is by using a scale. If you don't have one then fluff your flour with a spoon, sprinkle it into your measuring cup, and use a knife to level it off.
Do not over-mix the batter! The key to a light fluffy cake is mixing until Just combined, otherwise you'll activate the gluten in the flour and your cake will be dense and gummy.
You can add other spices to the filling like nutmeg, allspice or even cardamom.
Chopped candied or toasted pecans can be sprinkled over the icing for added crunch and visual appeal.
When you enjoy this cake the next day give it 20 seconds in the microwave to warm up the butter in the batter. If will have that fresh out of the oven tenderness and be that much more delicious.