Raspberry-Rhubarb Slab Pie

This Raspberry-Rhubarb Slab Pie is a celebration of spring and summer flavors. The vibrant combination of sweet raspberries and tart rhubarb creates a luscious filling that’s perfectly balanced, while the large slab format makes it easy to serve a crowd. With its flaky buttery crust and generous portion of fruit, this pie is as impressive as it is delicious.

Ingredients
For the Crust
3 cups all-purpose flour
1 tablespoon granulated sugar
1 teaspoon salt
1 cup (2 sticks) unsalted butter, cold and cubed
½ to ¾ cup ice water
For the Filling
4 cups sliced fresh rhubarb (about 1 lb)
2 cups fresh or frozen raspberries
¾ cup granulated sugar (adjust based on sweetness of fruit)
¼ cup light brown sugar
2 tablespoons cornstarch
1 teaspoon lemon juice
½ teaspoon ground cinnamon
¼ teaspoon salt
For the Egg Wash and Topping
1 large egg, beaten with 1 tablespoon water
Coarse sugar (optional, for sprinkling on top)
Instructions
Step 1: Make the Pie Dough
In a large mixing bowl, whisk together the flour, sugar, and salt.
Add the cold cubed butter and use a pastry cutter or your fingers to work it into the flour mixture until it resembles coarse crumbs with some pea-sized pieces of butter remaining.
Gradually add the ice water, one tablespoon at a time, mixing gently with a fork until the dough comes together. Be careful not to overwork it.
Divide the dough in half, shape each half into a disk, wrap tightly in plastic wrap, and refrigerate for at least 1 hour (or up to 2 days).
Step 2: Prepare the Filling
In a large mixing bowl, combine the sliced rhubarb, raspberries, granulated sugar, brown sugar, cornstarch, lemon juice, cinnamon, and salt. Stir gently to coat the fruit evenly.
Let the filling sit for 15-20 minutes to allow the juices to release, then stir again.
Step 3: Assemble the Pie
Preheat your oven to 400°F (200°C). Line a large baking sheet with parchment paper for easier cleanup.
On a lightly floured surface, roll out one piece of chilled dough into a rectangle about 1/8-inch thick. Transfer it to the prepared baking sheet.

1. Pour the fruit filling onto the dough, leaving a 1- to 1½-inch border around the edges. Fold the exposed edges of the dough up and over the filling, pleating as needed to create a rustic edge.
2. Roll out the second piece of dough and cut it into strips for a lattice topping, or simply place it on top of the filling and crimp the edges to seal. Brush the entire crust with the egg wash and sprinkle with coarse sugar if desired.