Ingredients
6 tbsp. unsalted butter, melted, plus room-temperature butter for pan
1 c. all-purpose flour
1/2 c. packed light-brown sugar
1/4 tsp. salt
1/2 lb. rhubarb
1 tbsp. light-brown sugar
1 c. all-purpose flour
1/2 tsp. baking powder
1/4 tsp. salt
1/2 c. unsalted butter
1 c. confectioners’ sugar
2 large eggs
1/2 tsp. pure vanilla extract
Preparation
Step 1Preheat oven to 350 degrees F. Butter an 8-inch square baking pan. Line with parchment paper, leaving a 2-inch overhang on two sides. Butter and flour parchment and pan, tapping out excess flour.Step 2Make streusel: Whisk together butter, brown sugar, and salt. Add flour and mix with a fork until large crumbs form. Refrigerate until ready to use.Step 3Make cake: In a medium bowl, combine rhubarb, brown sugar, and 1/4 cup flour. In another medium bowl, whisk 3/4 cup flour, baking powder, and salt. In a large bowl, using an electric mixer, beat butter and confectioners’ sugar until light and fluffy; beat in eggs, one at a time. With mixer on low, beat in vanilla, then flour mixture. Spread batter in prepared pan. Sprinkle with rhubarb and top with streusel.Step 4Bake cake until golden and a toothpick inserted in center comes out with moist crumbs attached, 45 to 50 minutes. Let cool completely in pan. Using paper overhang, lift cake from pan. Cut into 16 bars.
