Coffee Cake -
Preheat the oven to 350 degrees F. Grease and flour a 10-inch bundt or tube pan.
Cream 1-1/2 sticks of room temperature butter and 1-1/2 cups of granulated sugar in a bowl of an electric mixer fitted with the paddle attachment for 4 to 5 minutes, until light. Add the eggs 1 at a time 3 extra large eggs at room temperature, when eggs are thoroughly mixed in, add 1-1/2 teaspoons of pure vanilla extract and 1-1/4 cups of sour cream. And please in the name of all that is good, do not use low fat or fat free sour cream! In a separate bowl, sift together 2-1/2 cups of all-purpose flour, 2 teaspoons of baking powder, 1/2 teaspoon baking soda, and 1/2 teaspoon of salt. With the mixer on low, add the flour mixture to the batter until just combined. Scrape down the sides of the bowl with a spatula and stir to completely mix the batter.
For the cinnamon swirl, in a separate medium size bowl add 1/4 cup brown sugar (dark or light), 1/2 cup all-purpose flour, 1-1/2 teaspoons ground cinnamon, 1/4 teaspoon salt, and 3 tablespoons COLD butter in a bowl. Pinch the mixture together with your fingers until it forms small crumbles. You can mix in 3/4 cups of pecans or walnuts at this point, if desired.
Spoon half the batter into prepared cake pan and spread it out with a knife. Sprinkle with 3/4 cup streusel. Spoon the rest of the batter in the pan, spread it out, and scatter the remaining streusel on top. Bake for 55 to 60 minutes, until a toothpick comes out clean.
Let the cake cool on a wire rack for at least 30 minutes. Carefully transfer the cake, streusel side up, onto a serving plate.
Whisk together 2 tablespoons melted butter, 1/2 cup confectioners' sugar 1 teaspoon pure vanilla extract, 1/4 teaspoon ground cinnamon and 3 to 6 tablespoons water. You want the glaze to be thick but also just a little runny. Drizzle as much as you like over the cake with a fork or spoon.
Serve on a plate and feel unguilty because there's no chocolate in this cake!