Icelandic Rhubarb Bars | Saveur

Ingredients

• 1½ lb. rhubarb, sliced into 1-in. lengths, divided (about 2 cups)
• ½ cup turbinado sugar
• Pinch salt
• Two 2-in. pieces of red beet, optional (see headnote)
• 2¾ cups all-purpose flour
• 2½ cups quick oats
• 2 tsp. baking soda
• 1½ cups turbinado sugar
• 1¼ tsp. kosher salt
• 2 large eggs, at room temperature
• 27 Tbsp. unsalted butter, at room temperature, cubed
• 1 Tbsp. whole milk
• 2 egg yolks
• 1½ cups all-purpose flour
• 1¼ cups light or dark brown sugar
• 18 Tbsp. unsalted butter, at room temperature, cubed
• 1¼ cups quick oats
• 1 cup rolled oats