Preheat the oven to 325 degrees F, and mist a 9x9-inch metal pan with non-stick spray.
Place the flour, sugar, baking powder, baking soda, and salt in the bowl of an electric mixer, and stir to combine.
Add the butter, and mix on medium-low speed until the mixture resembles damp sand (about 2 minutes).
Add the eggs, one at a time, mixing on low speed until smooth.
Scrape the bottom and sides of the bowl with a silicone spatula, then add the sour cream, vanilla, and lemon juice.
Beat on medium speed for about 1 ½ minutes, to aerate the cake batter and build its structure.
Transfer the cake batter to the prepared pan.
Layer the cinnamon crumb mixture on top, then bake the cake for 30 to 40 minutes, or until a toothpick inserted in the thickest part of the cake comes out clean or with a few moist crumbs.
Cool completely, then dust with powdered sugar for garnish.