Step 1

Heat oven to 400° F. In a food processor, combine the flour, salt, and 1 tablespoon of the sugar. Add the butter and pulse until the mixture resembles coarse meal. Add cold water, 1 tablespoon at a time, and pulse until the dough comes together but is still slightly crumbly (you should use 3 to 4 tablespoons total). Turn the dough onto a lightly floured surface and knead gently. Shape the dough into a disk, wrap it in plastic, and refrigerate for 20 minutes.

Step 2

Meanwhile, in a large bowl, combine the rhubarb, raspberries, and 1 cup of the remaining sugar; set aside.

Step 3

On a lightly floured surface, roll the dough into a 14-inch circle. Place it in a large cast-iron skillet, allowing the dough to hang over the edge. Top with the rhubarb mixture. Fold the edge of the dough over the fruit (to create pleats).

Step 4

Lightly brush the top of the dough with water and sprinkle with the remaining sugar. Bake until golden brown, 50 to 55 minutes. Let cool for 5 to 10 minutes. Slice into wedges and serve with the whipped cream or ice cream (if using).