This cake comes from my sister Peg via one of our favorite cookbooks, Recipes from a Very Small Island. The batter is of the highest order, and the cake a light, moist texture (I substitute the sour cream with yogurt). Don’t let the bit of shortening scare you off. Assuming none of us eat very much of it in general, a little in your cake here won’t hurt! The rhubarb makes a perfect tart addition the brown sugar sweetness of the cake.
Preheat the oven to 350 degrees F. Grease and flour a 13x9x2-inch pan with one tablespoon of the butter.
In a small bowl, combine the tablespoon of melted butter, granulated sugar, walnuts, and cinnamon to form a crumble. Set aside.
In a stand mixer fitted with the paddle attachment, or using a hand mixer, beat the brown sugar, shortening, and egg on medium speed until light and creamed.
In another bowl, whisk the flour, baking soda and salt.
With the mixer on low speed, alternate adding the yogurt and the flour mixture in a few additions each, beating until a thick batter forms.
Using a spatula, fold in the chopped rhubarb. Scrape the batter into the prepared baking pan and spread the batter evenly in the pan. Top evenly with the nut crumble.
Bake for 40 to 50 minutes, or until the cake is golden brown and a toothpick inserted in the center comes out clean. Cool completely and serve in squares directly from the pan.