Preheat oven to 350°.
Cream butter and the sugar together slowly. Add one cup of the sugar at a time. You do not want the consistency and feel of sand. You want it light and fluffy. .
Beat in the eggs one at a time
Fold in the sour cream and pure vanilla.
In another bowl sift the flour, baking powder and salt.
Mix into the butter mixture.
In another small bowl, combine the topping ingredients; sugar, pecans and cinnamon.
Butter and flour the Bundt pan really well. Cover every inch and crevice thoroughly.
Pour about half the batter into a bundt pan.
Sprinkle with half the pecan topping mixture.
Spoon in the remaining batter.
Top with the remaining topping mixture.
Bake in the oven for 45 minutes then start testing every five minutes until it's done. It's done when the cake tester or toothpick when inserted in the middle comes out clean.
While the cake is cooling, you can prepare the drizzle. In a medium sized bowl, add in the butter, powdered sugar, vanilla, and 2 tbsps at a time of the water until you get to the consistency that you are looking for. Then pour over the cooled cake.