If you’re looking for a dessert that truly captures the vibrant, tangy sweetness of summer, the Raspberry-Rhubarb Slab Pie is your answer. This cheerful, crowd-pleasing treat layers tart rhubarb and juicy raspberries between buttery, golden sheets of flaky pastry, then bakes it all into a convenient slab format that’s perfect for potlucks, picnics, or just sharing at home. Each bar delivers a bit of nostalgia and a burst of seasonal flavor, making it nearly impossible to stop at one slice. It’s a favorite I come back to year after year, and I can’t wait to show you how easy it is to bake your own Raspberry-Rhubarb Slab Pie!
Ingredients You’ll Need
Gathering your ingredients for Raspberry-Rhubarb Slab Pie couldn’t be simpler, but every component plays a crucial role in creating a dessert that’s as beautiful as it is delicious. From the freshness of the fruit to the cold cubes of butter for the pastry, you’ll appreciate how each ingredient lends character and color to the final bake.
- All-purpose flour: The structure and backbone for your flaky, tender crust.
- Granulated sugar: Sweetens both your pastry and filling, balancing the tartness of the rhubarb.
- Salt: Just a pinch highlights flavors and ensures your crust isn’t bland.
- Unsalted butter (cold and cubed): The secret to wonderfully crisp and flaky pastry layers — keep it cold for best results.
- Ice water: Helps the dough come together without making it tough, ensuring a tender bite.
- Fresh rhubarb (chopped): Provides a tangy freshness and gorgeous pink hue to the filling.
- Fresh raspberries: Bring juicy sweetness and vibrant color that complements the rhubarb perfectly.
- Cornstarch: Thickens the filling so you get luscious, not runny, pie bars.
- Lemon juice: Brightens all the flavors and keeps everything tasting fresh.
- Vanilla extract: Adds a subtle warmth and aroma to the filling.
- Butter (for dotting): Melts into the fruit as it bakes, enriching the filling.
- Egg (beaten, for egg wash): Brushed over the top for a shiny, golden crust.
- Coarse sugar for sprinkling (optional): Adds sparkle and a lovely crunch to the finished pie.
How to Make Raspberry-Rhubarb Slab Pie
Step 1: Prepare the Pie Dough
Start by whisking together the flour, a touch of sugar, and salt in a large bowl. Cut in the cold, cubed unsalted butter until the mixture looks like coarse crumbs — use a pastry cutter or your fingers for this tactile step. Then, add ice water a tablespoon at a time, mixing gently until the dough just comes together. Divide the dough in half, shaping each piece into a rough rectangle. Wrap and chill them for at least 30 minutes; this resting time is key for a tender, flaky crust.
Step 2: Mix the Fruit Filling
While the dough chills, stir together your chopped rhubarb and raspberries along with the sugar, cornstarch, lemon juice, and vanilla extract. This combination gets juicy fast, so give it a gentle stir so the berries stay mostly intact and everything is beautifully combined. The cornstarch is your friend here, working to catch all those glorious juices as the pie bakes.
Step 3: Roll Out and Assemble
Take one portion of your chilled dough and roll it out on a floured surface until it’s big enough to line the bottom and sides of your greased 10×15-inch baking sheet. Press it gently into the pan, getting into the corners. Pour the luscious raspberry-rhubarb filling over the crust and dot with small pieces of butter. Roll out the second dough rectangle and carefully lay it over the top, trimming and crimping the edges so everything stays neatly enclosed. Cut a few slits in the top to let steam escape — or get creative with lattice or cut-out shapes!
Step 4: Add the Finishing Touches
Brush the top crust with your beaten egg to help it bake up golden and beautiful. If you like a little extra sparkle and crunch, sprinkle with coarse sugar. Not only does this look gorgeous, but it adds a perfect bit of texture to every slice.
Step 5: Bake and Cool
Slide your assembled slab pie into a 400°F oven and bake for 35 to 40 minutes, until your kitchen smells like a dream and the crust is golden brown with bubbling fruit underneath. Resist the urge to slice right away — letting the Raspberry-Rhubarb Slab Pie cool completely ensures you get nice, clean bars and all the flavors have a chance to settle.
How to Serve Raspberry-Rhubarb Slab Pie
Garnishes
A freshly baked Raspberry-Rhubarb Slab Pie is plenty delicious on its own, but if you’re looking to dress it up, a dusting of powdered sugar or a scoop of vanilla ice cream works beautifully. A dollop of whipped cream on the side adds a wonderful lightness, and a few fresh raspberries or mint leaves sprinkled on top will make each slice downright irresistible.
Side Dishes
Pair your warm or chilled pie bars with a cold glass of lemonade or a mug of hot coffee for true comfort. For a brunch spread, serve slices alongside a fresh fruit salad or a tangy yogurt parfait — these light accompaniments balance the sweet-tart punch of the slab pie without overshadowing it.
Creative Ways to Present
Cut the cooled Raspberry-Rhubarb Slab Pie into bars or squares for easy, shareable treats — perfect for picnics and parties. For an elegant twist, use cookie cutters to make festive shapes from the cooled pie, or present smaller slices in cupcake liners for a fun, portable dessert option. A drizzle of simple glaze or white chocolate zigzag over each bar is another playful (and delicious) finishing touch.
Make Ahead and Storage
Storing Leftovers
If you somehow have leftovers — and that’s a big “if” — store them tightly covered at room temperature for a day or two, or refrigerate for up to four days. The crust keeps its pleasant bite, and the filling remains just as flavorful. For best results, use parchment or wax paper to separate layers if stacking the bars.
Freezing
The Raspberry-Rhubarb Slab Pie freezes like a dream. Once fully cooled, wrap individual slices or the whole slab tightly in plastic wrap and then in foil. Label and pop it in the freezer for up to three months. When ready to serve, thaw overnight in the refrigerator. The fruit stays bright, and the crust retains much of its fantastic texture.
Reheating
To revive that just-baked taste, reheat individual bars in a 325°F oven for 10 to 15 minutes until warmed through. Avoid the microwave, which can make the crust soggy. This simple step brings the Raspberry-Rhubarb Slab Pie back to life and makes it taste as fresh as the day you baked it.
FAQs
Can I use frozen fruit instead of fresh?
Absolutely! If you’re using frozen rhubarb or raspberries, don’t thaw them before mixing into the filling. Using them straight from the freezer helps prevent the filling from becoming too watery and preserves the texture you want in your Raspberry-Rhubarb Slab Pie.
How do I prevent a soggy bottom?
For a crisp bottom crust, make sure to bake the slab pie on the lower-middle rack and don’t skip the cornstarch in the filling; it’s essential for thickening those juicy berries and rhubarb. Also, letting the pie cool completely before cutting ensures the crust stays sturdy.
Can I substitute other berries?
Definitely! Blueberries or blackberries pair nicely with rhubarb if you don’t have raspberries on hand. Just keep the quantity the same for best results and enjoy a fun twist on the Raspberry-Rhubarb Slab Pie classic.
Do I need to peel the rhubarb?
Not at all! Fresh rhubarb doesn’t need peeling; just trim the ends and any tough strings if you notice them while chopping. The skin adds a wonderful color and contributes to the overall charm of your Raspberry-Rhubarb Slab Pie.
Can this recipe be halved?
Yes, if you want a smaller batch, simply halve all the ingredients and bake in a 9×9-inch pan. You’ll get a more petite but equally delightful version that still captures all the flavors of the original slab pie.
Final Thoughts
I hope you’ll treat yourself and your loved ones to this Raspberry-Rhubarb Slab Pie soon — it’s the kind of dessert that brings people together, no matter the season. Each slice is a celebration of tart and sweet, flaky and buttery, all in one easy-to-share bar. Whether for a picnic, a party, or just a well-deserved treat at home, this recipe is sure to become a favorite in your kitchen too.
Print
Raspberry-Rhubarb Slab Pie Recipe
- Prep Time: 45 minutes (includes chilling)
- Cook Time: 40 minutes
- Total Time: 1 hour 25 minutes
- Yield: 12 servings
- Category: Dessert
- Method: Baking
- Cuisine: American
- Diet: Vegetarian
Description
Indulge in the delightful combination of tart rhubarb and sweet raspberries in this easy-to-make Raspberry-Rhubarb Slab Pie. Perfect for feeding a crowd or enjoying leftovers, these pie bars are a summer dessert favorite.
Ingredients
- 2 1/2 cups all-purpose flour
- 1 tablespoon granulated sugar
- 1 teaspoon salt
- 1 cup unsalted butter (cold and cubed)
- 6–8 tablespoons ice water
- 3 cups fresh rhubarb (chopped)
- 2 cups fresh raspberries
- 1 1/4 cups granulated sugar
- 1/4 cup cornstarch
- 1 tablespoon lemon juice
- 1 teaspoon vanilla extract
- 1 tablespoon butter (cut into small pieces)
- 1 egg (beaten, for egg wash)
- Coarse sugar for sprinkling (optional)
Dough:
Filling:
Instructions
- Preheat the oven: Preheat the oven to 400°F and lightly grease a 10×15-inch rimmed baking sheet.
- Prepare the dough: Mix flour, sugar, and salt. Cut in butter, add ice water gradually, shape into rectangles, and chill.
- Make the filling: Combine rhubarb, raspberries, sugar, cornstarch, lemon juice, and vanilla.
- Assemble the pie: Roll out dough, place in pan, add filling, top with second dough, trim edges, and vent. Brush with egg wash and sugar.
- Bake: Bake for 35–40 minutes until golden and bubbly. Cool before slicing.
Notes
- If using frozen fruit, do not thaw before mixing.
- For a decorative top, use lattice strips or cut-out shapes from the top crust.
- Serve with vanilla ice cream or whipped cream for a summer dessert favorite.
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