Preheat oven to 350° F

Prepare two 8-inch pans, grease with butter and line bottom with parchment paper

for the filling:

Trim ends of rhubarb and slice into 1/2 inch pieces, toss with powdered sugar and 1/4 cup flour, set aside. The rhubarb will release juices while you prepare the other components

for the crumb:

Combine butter, brown sugar, 1/3 cup sugar, 1/3 cup flour, teaspoon vanilla, and a pinch of salt

for the cake:

Combine the sour cream, eggs, and 1 teaspoon vanilla

In another bowl, combine 2 cups flour, 3/4 cup sugar, baking soda, baking powder, and a pinch salt

Work in butter and add wet ingredients

In a food processor, process nuts with 3 tablespoons flour until fine, add to the cake batter, stirring until uniformly combined

Spread batter in prepared pans, top with rhubarb mixture, and crumble crumb topping over the rhubarb

Bake 50 – 55 minutes (internal temp 210° F), cool before serving