- 1/4 cup water
- 1 1/2 teaspoons cornstarch
- 1/3 cup plus 1/2 cup sugar
- 2 cups chopped fresh rhubarb stalks (10 ounces)
- 1 cup chopped fresh strawberries (5 ounces)
- 1 cup all-purpose flour
- 1 3/4 teaspoons baking powder
- 1/2 teaspoon salt
- 1 large egg
- 1/2 cup whole milk
- 1 stick (1/2 cup) unsalted butter, melted and cooled slightly
- 1 teaspoon pure vanilla extract
- Put oven rack in middle position and preheat oven to 400°F. Butter an 8-inch square glass or ceramic baking dish.
- Stir together water, cornstarch, and 1/3 cup sugar in a small saucepan, then stir in rhubarb. Bring to a simmer, stirring constantly, then simmer, stirring occasionally, 3 minutes. Remove from heat and stir in strawberries.
- Whisk together flour, baking powder, salt, and remaining 1/2 cup sugar in a bowl.
- Whisk together egg, milk, butter, and vanilla in a large bowl, then whisk in flour mixture until just combined.
- Reserve 1/2 cup fruit mixture, then add remainder to baking dish and pour batter over it, spreading evenly. Drizzle reserved 1/2 cup fruit mixture over batter. Bake until a wooden pick inserted into center of cake portion comes out clean, 25 to 30 minutes. Cool in pan on a rack 5 minutes before serving.