For the streusel:

1. Mix all dry ingredients, all the butter and work with your hands until it is clumpy with no dry spots.
2. Add pecans and mix. Reserve.

For the cake:

1. Preheat oven to 350ºF/180ºC.
2. Butter or spray a 10-inch simple bundt or tube cake pan (see Notes below) and line the bottom with parchment paper.
3. In a large bowl, cream butter and add sugar gradually, beating until creamy, 3 minutes. Use an electric mixer. 
4. Add vanilla and eggs, one at a time, beating well after each one.
5. Add the sifted dry ingredients (flour, baking powder, baking soda, and salt) in 3 parts, alternating with the sour cream in 2 parts. You start and end with flour. You can sift them before or have the ingredients measured and sift them directly over the butter mixture (my choice). 
6. Mix well but don't overbeat. The cake batter will be thick and velvety. 
7. Put half of this mixture in the prepared pan. Smooth it with the back of a damp spoon (it will glide more easily) and add half the streusel mixture over it.
8. Drop mounds of remaining batter mixture by tablespoons and carefully smooth it with the back of a spoon (if it sticks, dampen the spoon again). 
9. Sprinkle the remaining streusel over it.
10. Bake for 50-60 minutes, until a cake tester or toothpick comes out dry.
11. Let it cool on a wire rack for 10-15 minutes. Use a flat knife to carefully loosen the edges that might be stuck due to the sugar in the streusel.
12. Let cool completely on a wire rack before removing. Place a wire rack on top of the pan and carefully turn it upside down. 
13. Transfer to a plate and glaze. 

For the glaze:

1. Mix ingredients in a bowl until creamy.
2. Pour over cold cake and let drip down the sides.
3. It keeps for a few days, well wrapped, at room temperature.