Preheat your oven to 350°F (175°C). Grease and flour your Bundt pan to prevent sticking.
In a large mixing bowl, beat the softened butter and 1 ½ cups of sugar together using an electric mixer until the mixture is light and fluffy, about 3-5 minutes.
Add the eggs, one at a time, mixing well after each addition. Then, stir in the vanilla extract until fully combined.
In a separate bowl, whisk together the flour, baking powder, baking soda, salt, and ground cinnamon.
Gradually add the dry ingredients to the butter mixture, alternating with the sour cream. Start and end with the dry ingredients, mixing until just combined.
Gently fold in the chopped walnuts using a rubber spatula until evenly distributed throughout the batter.
Pour the batter into the prepared Bundt pan, spreading it evenly.
Bake in the preheated oven for 50-60 minutes, or until a toothpick inserted into the center comes out clean.
Allow the cake to cool in the pan for about 10-15 minutes before inverting it onto a cooling rack. Let it cool completely before slicing and serving.