Preheat oven to 350°F. Line a 9x9” pan with foil and spray with cooking spray.

Crush Nilla Wafers in a food processor. Stir with melted butter. Press crust into the botto of the pan. Bake for 8 minutes. Wipe out the bowl you used to mix the crust with a paper towel. Set aside to use when making the crumble.

Beat cream cheese, egg, and sugar with a stand or a hand mixer in a larger bowl. Mix in sour cream, lemon juice, zest, vanilla, and flour. Mix until smooth. The trick to getting your cheesecake smooth and not lumpy is to make sure all the ingredients are room temperature!

Make the crumble: mix the all crumble ingredients using a hand or stand mixer in a large bowl (which can be the same bowl as the one you made the crust in). The mixture will be stiff and crumbly.

Pour the cheesecake mixture over the partially baked hot crust. Sprinkle the crumble over the top. Bake for an additional 28-32 minutes until the edges are browned and the cheesecake is no longer glossy. Cool completely then cover and chill for at least 2 hours before serving.

Slice and store bars in an airtight container in the refrigerator for up to 3 days or freeze for up to 1 month.