Step 1- Preheat the oven to 350 degrees F.
Step 2- Grease and flour a 10-inch tube pan.
Step 3- Cream the butter and sugar in the bowl of an electric mixer until light. Add the eggs 1 at a time, then add the vanilla and sour cream.
Step 4- In a separate bowl, sift together the flour, baking powder, baking soda, and salt.
Step 5- With the mixer on low, add the flour mixture to the batter until just combined. Finish stirring with a spatula to be sure the batter is completely mixed.
Step 6- For the streusel, place the brown sugar, flour, cinnamon, salt, and butter in a bowl and pinch together with your fingers until it forms a crumble.
Step 7- Spoon half the batter into the pan and spread it out with a knife. Sprinkle with 3/4 cup streusel.
Step 8 -Spoon the rest of the batter in the pan, spread it out, and scatter the remaining streusel on top. Bake for 50 to 60 minutes.