Preheat the Oven and Prepare the Pan:

• Preheat your oven to 350°F (175°C).

• Grease a 9×13-inch baking pan with butter or non-stick spray. Set aside.

Make the Streusel:

• In a medium bowl, combine the flour, brown sugar, cinnamon, and salt. Mix well.

• Add the cold butter pieces and use a pastry cutter or your fingers to cut the butter into the dry ingredients until the mixture resembles coarse crumbs. Set aside.

Prepare the Cake Batter:

• In a large mixing bowl, cream the softened butter and granulated sugar together until light and fluffy, about 2-3 minutes.

• Add the eggs one at a time, mixing well after each addition. Stir in the vanilla extract.

• In a separate bowl, whisk together the flour, baking powder, baking soda, and salt.

• Gradually add the dry ingredients to the wet ingredients, alternating with the sour cream. Begin and end with the dry ingredients, mixing just until combined.

Assemble the Cake:

• Spread half of the cake batter evenly into the prepared baking pan.

• Sprinkle half of the streusel mixture over the batter.

• Carefully spread the remaining batter over the streusel layer.

• Top with the remaining streusel, spreading it evenly.

Bake the Cake:

• Bake in the preheated oven for 35-40 minutes, or until a toothpick inserted into the center comes out clean.

• Allow the cake to cool in the pan for at least 15 minutes before adding the glaze.

Make the Glaze:

• In a small bowl, whisk together the powdered sugar and milk until smooth.

• Drizzle the glaze over the slightly cooled cake.

Serve:

• Slice the cake into squares and serve warm or at room temperature.