¾cup(12 Tablespoons or 170 g) unsalted butter, softened, but still cool, cut into 1/2-inch pieces
1teaspoonvanilla extract
Rhubarb Filling
2cups(300 g) diced rhubarb
⅓cup(100 g) granulated sugar
1Tablespooncornstarch, or flour
1Tablespoonfresh lemon juice
Pinchof salt
Instructions
Preheat oven to 350℉. Line a 8×8 baking dish with parchment paper and set aside.
In the bowl of a stand mixer (or using a hand mixer), combine flour, oats, brown sugar, granulated sugar, baking powder and salt. Mix for 30 seconds until thoroughly combined. With the mixer on low, add the butter and vanilla extract. Mix until the mixture resembles coarse sand (about 2 minutes).
Transfer half the mixture to prepared pan. Use your hands or the back of a measuring cup to press mixture evenly into the bottom to form the crust. Bake crust for 20 minutes or until golden (keep the oven on).
While the crust bakes, make the rhubarb filling. In a saucepan over medium heat, bring rhubarb, sugar, cornstarch, and lemon juice to a boil. Stir constantly until mixture is thickened, about 2 minutes. Remove from heat. Cool slightly.
Spread rhubarb mixture over baked crust. Sprinkle remaining oat mixture evenly over the fruit layer.
Bake bars for 30 to 35 minutes or until the rhubarb bubbles and the top is golden brown. Allow bars to cool completely before removing from pan and cutting into 16 squares.
Notes
Store covered in an airtight container at room temperature for up to 5 days or in the refrigerator for a week.Freeze for up to 3 months. Wrap in plastic wrap and place in an airtight container in the freezer. Defrost in the refrigerator before bringing to room temperature.