Ingredients
1 1/2 pounds rhubarb, trimmed and cut diagonally into 3/4-inch pieces
2 pints (about 12 ounces) fresh raspberries
1 1/2 cups sugar
1/4 cup quick-cooking tapioca
Freshly grated zest and juice of 1/2 lemon
1/2 teaspoon, plus a pinch coarse salt
1 cup all-purpose flour
1/3 cup cake flour (not self-rising)
2 teaspoons baking powder
1/2 teaspoon baking soda
6 tablespoons cold unsalted butter, cut into small pieces
3/4 cup plain yogurt
2 to 3 tablespoons heavy cream
Creme fraiche, for serving
Preparation
Preheat oven to 400 degrees with rack in center. Line a rimmed baking sheet with parchment.
In a large bowl, stir together rhubarb, raspberries, 1 1/4 cups sugar, tapioca, lemon juice, and a pinch salt. Let stand 15 minutes, stirring once or twice. Divide filling among six 10-ounce baking dishes, or pour into a 2 1/2-quart baking dish.
In a medium bowl, whisk together both flours, remaining 1/4 cup sugar, baking powder, baking soda, lemon zest, and remaining 1/2 teaspoon salt. Cut in butter until mixture resembles coarse crumbs. Add yogurt, and stir with a fork until dough consistency resembles a thick cake batter.
Using a large spoon, top filling with dollops of dough, leaving a 1-inch border. Brush dough with cream. Transfer baking dishes to prepared baking sheet. Bake, rotating sheet halfway through, until biscuits are golden-brown and juices are bubbling, 35 to 40 minutes. (If browning too quickly, cover loosely with aluminum foil during the last 15 minutes of baking.) Cool on a wire rack, at least 1 hour. Serve warm or at room temperature with a dollop of creme fraiche.
