Cinnamon-Streusel Coffee Cake

Streusel topping and center:
1 3/4 cups flour
1 cup packed light brown sugar
1 1/4 tsp. ground cinnamon
coarse salt
1 1/2 sticks cold unsalted butter, cut into small pieces

Cake:
1 stick unsalted butter, room temperature
2 cups flour
1 1/4 tsp. baking powder
1/2 tsp. baking soda
coarse salt
1 cup granulated sugar
2 large eggs
1 1/2 tsp. vanilla extract
1 cup sour cream

Glaze:
1 cup confectioners' sugar
2 tsp. whole milk

1. Make the streusel topping: mix together flour, 3/4 cup brown sugar, 1 tsp. cinnamon, and 1 tsp. salt.  Cut in butter with a pastry cutter until small to medium clumps form.  Refrigerate until ready to use.
2. Make the streusel center: mix together remaining 1/4 cup brown sugar and 1/4 tsp. cinnamon.
3. Preheat oven to 350.  Make the cake: butter a 9-inch tube pan with a removable bottom.  Sift flour, baking powder, baking soda and 1/2 tsp. salt into a bowl.
4. Beat butter and granulated sugar with a mixer on medium speed until pale and fluffy, about 2 minutes.  Beat in eggs, 1 at a time, then vanilla.  Beat in flour mixture in 3 additions, alternating with sour cream, beginning and ending with flour.  Continue to beat until well combined.
5. Spoon half the batter into pan.  Sprinkle streusel center mixture evenly over batter.  Top with remaining batter, and spread evenly using an offset spatula.  Sprinkle streusel topping mixture evenly over batter.
6. Bake until cake is golden brown and a toothpick inserted into the center comes out clean, about 55 minutes (I had to bake it for 70 minutes because the streusel was so thick!).  Transfer pan to a wire rack and let cool completely.  Remove cake from pan and transfer to parchment.
7. Make the glaze: mix together confectioners' sugar and milk.  Drizzle over cake and let drip down sides.  Let stand for 5 minutes before serving.

(Martha Stewart recipe).