A Rustic Fruit Pie That’s Perfect for Sharing with Family and Friends

Looking for a dessert that’s as beautiful as it is delicious? This Raspberry-Rhubarb Slab Pie blends the perfect sweet-tart flavors of juicy raspberries and tangy rhubarb in a buttery, golden crust. It’s a rustic, large-format pie baked in a sheet pan—ideal for potlucks, backyard barbecues, holiday gatherings, or any time you want to feed a crowd.

Whether you’re a seasoned baker or new to homemade pies, this easy-to-follow recipe will guide you to success. So grab your apron and let’s bake up a dessert that’s guaranteed to impress!

Introduction

There’s something magical about the combination of raspberries and rhubarb. The tartness of the rhubarb balances beautifully with the natural sweetness of the raspberries, creating a filling that’s vibrant, juicy, and just the right amount of zingy. Paired with a flaky, homemade double crust, it’s the kind of pie that feels nostalgic yet fresh and exciting.

Unlike traditional round pies, this slab pie is baked in a 9×13-inch pan, which makes it easier to serve and perfect for larger groups. And because it can be sliced into neat squares or bars, it’s also great for packing into lunchboxes or serving at events.

Ready to wow your taste buds and your guests? Let’s get baking.

Tools, Yield & Baking Time

Tools You’ll Need:

Mixing bowls (large and medium)
Pastry cutter or fork (or clean fingers)
Rolling pin
Plastic wrap
9×13-inch baking pan
Sharp knife or pizza cutter (for lattice, optional)
Pastry brush
Measuring cups and spoons

Serves:

12–15 slices, depending on how you cut the slab

Prep Time:

30 minutes (plus 1 hour for chilling dough)

Bake Time:

45–50 minutes

Total Time:

Approximately 2 hours and 20 minutes

Ingredients

For the Pie Dough:

2½ cups all-purpose flour
1 teaspoon salt
1 teaspoon granulated sugar
1 cup (2 sticks) unsalted butter, cold and cubed
6 to 8 tablespoons ice water

For the Filling:

3 cups rhubarb, chopped into ½-inch pieces
2 cups fresh raspberries
1 cup granulated sugar
¼ cup cornstarch
1 tablespoon lemon juice
1 teaspoon vanilla extract

For the Topping:

1 egg (for egg wash)
1 tablespoon coarse sugar (optional, for sprinkling)

Step-by-Step Instructions

Step 1: Make the Pie Dough

In a large mixing bowl, whisk together the flour, salt, and sugar. Add the cold, cubed butter and use a pastry cutter or your fingers to cut it into the flour until the mixture resembles coarse crumbs. This process helps create a flaky crust.

Gradually add the ice water, one tablespoon at a time, mixing gently until the dough begins to come together. You may not need all 8 tablespoons—stop once the dough holds together without being wet or sticky.

Divide the dough in half, shape each half into a flat disk, wrap in plastic wrap, and refrigerate for at least 1 hour to let the gluten relax and the butter firm up.

Step 2: Prepare the Filling

While the dough is chilling, prepare the fruit filling. In a medium bowl, combine the rhubarb, raspberries, sugar, cornstarch, lemon juice, and vanilla extract. Stir gently to evenly coat the fruit without breaking the raspberries. Set aside to macerate slightly.

Step 3: Preheat the Oven and Prepare the Pan

Preheat your oven to 375°F (190°C). Lightly grease a 9×13-inch baking pan with butter or nonstick spray.

Step 4: Roll Out the Bottom Crust

On a floured surface, roll out one dough disk into a rectangle slightly larger than the size of your pan. Carefully transfer the rolled dough to the baking pan, pressing it into the bottom and corners and letting the excess hang over the edges.

Step 5: Add the Filling

Give the fruit filling one last gentle stir, then pour it into the prepared crust, spreading it out evenly.

Step 6: Add the Top Crust

Roll out the second dough disk and place it over the filling in one of two ways:

Classic Top Crust: Lay the whole sheet over the filling.
Lattice Top: Cut the dough into strips and weave them across the top in a crisscross pattern.

Once the top crust is in place, trim the excess dough and crimp the edges with your fingers or a fork to seal.

Step 7: Finish and Bake

Beat the egg and brush it over the top crust for a beautiful golden finish. If desired, sprinkle with coarse sugar for extra crunch and sparkle.

Place the pan in the oven and bake for 45 to 50 minutes, or until the crust is golden and the filling is bubbling.

Step 8: Cool and Slice

Remove the pie from the oven and let it cool completely in the pan. This step is important to help the filling set. Once cool, slice into squares or bars and serve.

Tips for Raspberry-Rhubarb Slab Pie Success

1. Keep Everything Cold

Chilling the dough helps prevent shrinking and promotes flakiness. Cold butter is essential—don’t skip this step.

2. Use Fresh, Not Frozen Fruit

Frozen raspberries or rhubarb tend to release too much liquid, which can result in a runny filling. Fresh fruit works best for the right consistency.

3. Don’t Skip the Cornstarch

Cornstarch thickens the filling as it bakes, ensuring that your pie slices hold together well once cooled.

4. Let It Cool Completely

As tempting as it is to dig in while warm, the filling will be too soft. Allowing it to cool fully helps it firm up and makes slicing much easier.

5. Customize Your Crust

Feel free to get creative with decorative edges, lattice tops, or even small cookie cutter shapes layered on top. It’s a fun way to personalize your pie!

Serving and Storage Tips

How to Serve:

Serve at room temperature or slightly warmed.
Top with a scoop of vanilla ice cream or a dollop of whipped cream for an extra treat.
Pair with coffee or tea for an elegant dessert course.

How to Store:

At Room Temperature: Cover tightly and store for up to 2 days.
In the Refrigerator: Store in an airtight container for up to 5 days.
In the Freezer: Wrap tightly in foil and freeze for up to 3 months. Thaw in the fridge and reheat in a low oven before serving.

Frequently Asked Questions

1. Can I use store-bought pie crust?

Yes, you can use two sheets of store-bought pie dough if you’re short on time. The homemade version is flakier and more flavorful, but store-bought dough works well in a pinch.

2. Can I substitute other fruits?

Absolutely. Try swapping the raspberries with strawberries or blackberries. Blueberries also pair nicely with rhubarb.

3. Why is my filling runny?

If your filling is too liquidy, it may be due to excess moisture from the fruit or not enough thickener. Make sure to measure the cornstarch accurately and let the pie cool fully before cutting.

4. Do I need to peel rhubarb?

Not necessarily. As long as your rhubarb is tender and fresh, you don’t need to peel it. Just wash it well and chop into small pieces.

5. How do I make this pie vegan?

To make this recipe vegan, use a plant-based butter alternative in the crust and skip the egg wash. You can brush the top with a little almond milk instead.

Conclusion

This Raspberry-Rhubarb Slab Pie is a delightful way to celebrate the bright flavors of summer fruits in a format that’s perfect for sharing. With its buttery crust and tangy-sweet filling, every bite delivers a satisfying balance of flavors and textures.

Whether you’re making this for a special gathering or a simple weekend dessert, it’s sure to bring joy to anyone lucky enough to grab a slice.

So go ahead—try this recipe today, enjoy the baking process, and don’t forget to savor the sweet rewards. Happy baking!