• 2 pounds rhubarb , cut into 1-inch pieces (about 6 cups)
• 1 1/4 cups granulated sugar
• 1 1/4 cups all-purpose flour
• 1 tsp. vanilla extract
• 1 cup light brown sugar
• 1 stick unsalted butter , cut into small pieces
• 1/2 tsp. salt
• Vanilla ice cream , for serving (optional)

Preheat oven to 375°. To make filling, put rhubarb, granulated sugar, 1/4 cup flour, and vanilla into a 9" x 13" baking dish and toss well to combine; set aside.

To make crumble topping, put remaining 1 cup flour, light brown sugar, butter, and salt into a large bowl and toss well. Using your fingertips, rub butter into dry ingredients until mixture resembles coarse meal. Working with one small handful at a time, squeeze dough together to make a ball, then gently break it into chunks and scatter them on rhubarb filling in baking dish.

Bake until rhubarb is very tender and bubbly and crumble topping is golden brown, about 30 minutes. Serve warm with vanilla ice cream if desired; spoon any leftovers into bowls and eat cold for breakfast.