Rhubarb Brown Butter Bars - Oryana

Ingredients

• Zest of 1 grapefruit (about 1 tablespoon)
• Juice of ½ grapefruit
• 1 tablespoon dried hibiscus flowers (optional, but recommended)
• ¾ cup granulated sugar
• ¼ teaspoon kosher salt
• ¼ teaspoon vanilla bean paste (or ½ teaspoon vanilla extract)
• 1 lb rhubarb, sliced into ½ inch thick pieces (about 4 cups), divided
• 1¼ cups hazelnuts
• ¾ cup (1½ sticks) unsalted butter, cut into pieces
• 1¼ cups all-purpose flour
• 1¼ cups old-fashioned oats
• ¼ cup plus 1 tablespoon dark brown sugar, packed
• ¼ cup granulated sugar
• 1 teaspoon salt
• ½ teaspoon baking soda