Preheat your oven to 350 degrees and grease a bundt pan or angel food pan.
Blend together the granulated sugar, ½ cup of butter, eggs, sour cream and vanilla.
Sift together the flour, baking powder, baking soda and salt.
Stir the flour mixture into the creamed butter mixture and beat well.
Put half the batter into the bundt pan
Mix the brown sugar, nuts (if using), cinnamon and 2 Tbsp. of butter well (the original recipe says to use a pastry blender but I used a whisk with great success).
Sprinkle half of the brown sugar mixture onto the batter in the pan. top with the rest of the batter and then sprinkle the remaining brown sugar mixture on top.
Bake for 45-50 minutes or until your cake tester comes out clean.
Let it cool for a couple of minutes and then turn it onto your serving plate while it's still warm (a fellow reader noted having trouble with it sticking if you let it cool all the way) and enjoy!