Preheat the oven to 350°F (175°C). Grease and flour a 9-inch round or square baking pan.
In a medium bowl, whisk together 2 cups flour, baking powder, baking soda, and salt. Set aside.
In a large bowl, beat the softened butter and granulated sugar together with an electric mixer until light and fluffy, about 3 minutes.
Add the eggs one at a time, beating well after each addition.
Mix in the sour cream, lemon zest, lemon juice, and vanilla extract until combined.
Gradually add the dry ingredients to the wet ingredients, mixing just until combined. Do not overmix.
Prepare the streusel topping by combining brown sugar, 1/3 cup flour, and cinnamon in a small bowl. Cut in the cold butter with a pastry cutter or fork until the mixture resembles coarse crumbs.
Spread the cake batter evenly into the prepared pan.
Sprinkle the streusel topping evenly over the batter.
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, lemon juice, and lemon zest in a small bowl until smooth.
Remove the cake from the oven and allow it to cool in the pan for 15 minutes.
Drizzle the lemon glaze over the warm cake.
Let the cake cool completely before slicing and serving.