Preheat the oven to 350°F (175°C). Grease and flour a 9-inch round cake pan.
In a large bowl, whisk together 2 cups flour, granulated sugar, baking powder, baking soda, and salt.
In a separate bowl, beat the softened butter until creamy. Add eggs one at a time, beating well after each addition.
Mix in the sour cream, 1/4 cup lemon juice, lemon zest, and vanilla extract until combined.
Gradually add the dry ingredients to the wet ingredients, mixing until just combined. Do not overmix.
Prepare the streusel topping by combining brown sugar, cinnamon, 1/2 cup flour, and cold cubed butter in a small bowl. Use a pastry cutter or your fingers to blend until the mixture resembles coarse crumbs.
Pour half of the batter into the prepared cake pan and spread evenly.
Sprinkle half of the streusel topping over the batter.
Pour the remaining batter over the streusel layer and spread evenly.
Top with the remaining streusel mixture.
Bake for 40 to 45 minutes, or until a toothpick inserted into the center comes out clean.
While the cake is baking, prepare the lemon glaze by whisking together powdered sugar, 2 tablespoons lemon juice, and 1 teaspoon lemon zest until smooth.
Remove the cake from the oven and let it cool in the pan for 10 minutes.
Transfer the cake to a wire rack and drizzle the lemon glaze over the top while the cake is still warm.
Allow the glaze to set before slicing and serving.