This cozy rhubarb coffee cake layers tart fruit, tender crumb, and a cinnamon-sugar streusel for the perfect anytime treat.

—Recipes by Chef Steph

INGREDIENTS

• 1 pound rhubarb (5 or 6 (6-inch) stalks)
• 1 large lemon
• 1 2/3 cups packed light brown sugar, divided
• 3 tablespoons cornstarch
• 1 1/4 cups water, divided
• 12 tablespoons (1 1/2 sticks) cold butter, divided
• 1 (15.25-ounce) box vanilla or yellow cake mix
• 3 large eggs
• 2 teaspoons ground cinnamon

DIRECTIONS      

1. Arrange a rack in the middle of the oven and heat the oven to 350°F. Line an 8x8-inch baking pan with parchment paper so that it hangs off two sides to form a sling. Cut 1 pound rhubarb crosswise into 1/2-inch pieces (about 3 1/2 cups) and juice 1 large lemon.
   
2. Place the rhubarb, lemon juice, 1/3 cup packed light brown sugar, 3 tablespoons cornstarch, and 1/4 cup of the water in a small saucepan. Bring to a simmer over medium heat and cook until the rhubarb is slightly tender and the mixture is thick enough to coat the back of a spoon, 2 to 3 minutes. Remove from the heat and set aside to cool while you prepare the cake mix.
   
3. Place 8 tablespoons (1 stick) unsalted butter in a large microwave-safe bowl and microwave on high power in 10-second increments until melted. (Alternatively, melt on the stove, then pour into a large bowl.) Set aside 1/4 cup of the cake mix. Add the remaining cake mix, remaining 1 cup water, and 3 large eggs to the butter and whisk until smooth.
   
4. Place the remaining 1 1/3 cups packed light brown sugar, reserved cake mix, and 2 teaspoons ground cinnamon in a medium bowl. Cube the remaining 4 tablespoons unsalted butter and add to the brown sugar bowl. Using your fingers, press the butter into the dry ingredients until small clumps form.
   
5. Pour half of the cake batter into the prepared baking pan. Evenly distribute the cooled rhubarb mixture over the top. Top with remaining cake batter and smooth into an even layer. Sprinkle with the topping. Bake until the cake is lightly browned and a toothpick inserted into the center comes out clean, 35 to 45 minutes. Place the pan on a wire rack and let cool to room temperature. Grasping the parchment, lift the slab out of the baking dish and place onto a cutting board. Cut into 16 pieces.