SERVES 6 TO 8
The marionberry is a specific and majestic kind of blackberry that grows in a concentrated area around Salem, Oregon. It looks like an elongated blackberry; if you can’t get them where you are, blackberries are a perfect substitute.
1 cup sugar plus more for sprinkling
2 tablespoons cornstarch
1 cup water
1 quart (about 1 pound) marionberries, fresh or frozen, or substitute blackberries
4 tablespoons unsalted butter
1½ cups all-purpose flour
1 tablespoon baking powder
1 teaspoon kosher salt
⅔ cup milk
Preheat the oven to 350°F. Spray a 9-by-9-inch baking pan with cooking spray.
In a large saucepan over medium-high heat, combine ¾ cup of the sugar and the cornstarch, then add the water and bring to a boil. Add the berries and return to a boil. When the mixture thickens, about 10 minutes, pour into the prepared pan.
In a stand mixer with the paddle attachment or a large bowl with an electric mixer, cream the butter with the remaining ¼ cup sugar. Mix together the flour, baking powder, and salt. Beat the flour mixture into the butter mixture and then gradually add the milk, beating until well combined.
Drop dollops of the batter over the surface of the berries. Lightly sprinkle pinches of sugar over the batter. Bake for 45 minutes, until the batter has browned. Serve warm.