In a large bowl, combine 3 cups sifted flour, 1 ½ teaspoon baking soda, 1 ½ teaspoon baking powder and ½ teaspoon salt. Whisk together and set aside.
In the bowl of a standing mixer or other large mixing bowl (if using stand mixer, use paddle attachment), cream ¾ cup butter with 1 ½ cups sugar until light and fluffy. Add 2 teaspoons vanilla. Add 3 eggs one at a time, beating after each one. Scrape sides of bowl and beat at high speed until mixture is light and creamy, about one minute.
On low speed, add dry ingredients in three additions alternating with sour cream in two additions. Beat only until smooth after each addition.
Spread your first layer of batter in bottom of prepared pan. This is easier to do if you use a small spoon to drop batter into pan and then smooth it together. Top with ⅓ of the nut mixture (it is okay if it spreads to touch the pan). Repeat until you have four layers of batter and three layers of nut filling. The top layer will be batter.
Place pan in oven on center rack (never put a Bundt pan on a tray. Air needs to circulate through the hole in the center of the Bundt pan).
Bake until a toothpick or skewer comes out with a few crumbs, about 44-48 minutes. Remove and let cool on rack for 5 minutes.
Invert cake onto a cooling rack and remove pan. Place a baking pan under the cooling rack.
Turn oven back on to a High Broil setting and place oven rack one slot below the middle.