Preheat oven to 350 degrees. Spray a 9" spring form pan with non-stick baking spray, and set aside. In a bowl, add flour, baking powder and salt. Whisk together and set aside.
In another bowl, combined the soft butter, flour and brown sugar. Mixture will be crumbly. Evenly sprinkle/crumble the streusel over the top of the batter.
Bake at 350 for 1 hour, 15 minutes. Ensure the cake is set and cooked through by lightly moving the pan. If the batter giggles, its not done. Batter needs to be set, golden brown, and when inserting a toothpick, it should come out clean of crumbs.
Take out of the oven, let cool for about 15 minutes before removing from the pan. To make the glaze, combine the lemon juice and powdered sugar. Stir until fully combined and drizzle over the cake.