A great choice to serve with coffee or tea. Adapted from Bon Appetit magazine. This has a very mild lemon flavor and is not overly sweet- if you prefer more of a lemony punch, add a teapsoon of lemon flavor extract along with the vanilla.
Combine flour, both sugars,lemon zest, and cinnamon.
Add oil and lemon juice and stir just until dry ingredients are all moistened and starts to clump up (mixture should have lots of large clumps of varying sizes, as well as some smaller pea sized lumps - it should be very lumpy, not fine).
Scoop out 1 cup of this mixture and set aside in a small bowl- this will be your crumb topping.
Whisk together sour cream, egg, vanilla, baking powder, and baking soda well.
Using a mixer, add sour cream mixture to clumpy mixture still in mixing bowl and beat until smooth.
Pour into pan, spreading with a spatula until even.
Sprinkle reserved clumpy mixture over the top.
Bake about 40 minutes or until cake tester comes out clean.
Let cool in pan on wire racks.
Before serving, sprinkle with powdered sugar, then cut into squares and serve.