01 - Preheat oven to 350°F. Grease and flour an 8-inch cake pan.
02 - Combine flour, sugar, lemon zest, and salt. Add cold butter, working it in with fingers or pastry cutter until coarse crumbs form. Refrigerate until needed.
03 - Whisk flour, baking powder, baking soda, and salt in a medium bowl.
04 - Beat softened butter and sugar until light and fluffy, about 2 to 3 minutes. Add eggs one at a time, mixing well after each addition.
05 - Stir in sour cream, milk, lemon juice, lemon zest, and vanilla extract until just combined.
06 - Gently fold the dry ingredients into the wet mixture until just incorporated. Avoid overmixing.
07 - Spread batter evenly into the prepared pan. Sprinkle crumble topping uniformly over the batter.
08 - Bake for 38 to 42 minutes, or until a toothpick inserted in the center comes out clean and the top is golden brown. Let cool in the pan for at least 15 minutes.
09 - Mix powdered sugar with enough lemon juice to create a drizzle consistency. Drizzle over cooled cake before serving.