01 - Preheat the oven to 350°F. Grease and flour a 9-inch round or square cake pan.
02 - Combine flour, sugar, cinnamon, and salt in a small bowl. Cut in cold butter with a fork until coarse crumbs form. Refrigerate until needed.
03 - Beat butter and sugar until light and fluffy. Add eggs one at a time, beating after each addition. Stir in lemon zest, lemon juice, sour cream, milk, and vanilla extract until smooth.
04 - Whisk flour, baking powder, baking soda, and salt together separately. Gradually fold into wet mixture, mixing until just combined.
05 - Pour batter into prepared pan and smooth surface. Evenly sprinkle crumble topping over batter.
06 - Bake for 38 to 42 minutes or until a toothpick inserted in the center comes out clean.
07 - Allow cake to cool in pan for 10 minutes, then transfer to a wire rack to cool completely.
08 - Whisk powdered sugar and lemon juice until smooth. Drizzle over cooled cake before serving.