Serves 10 to 12
- 1 1/4 cups chopped walnuts
- 2 sticks (8 ounces) unsalted butter, softened to room temperature
- 1/2 cup (packed) dark or light brown sugar
- 1/2 cup granulated sugar
- 1 3/4 cups all-purpose flour
- 3/4 teaspoon ground cinnamon
- 1/4 teaspoon baking powder
- 1/8 teaspoon salt
- 3 pounds fresh rhubarb
- 1 cup plus 2 tablespoons granulated sugar
- 3 tablespoons all-purpose flour
- Dash of salt
- Finely grated zest of 1 California-grown orange
- 1 tablespoon fresh orange juice
Preheat oven to 350 degrees. Spread nuts on a baking sheet and bake, stirring once or twice, until lightly browned and fragrant, 5 to 7 minutes. Let cool.
Using an electric mixer or a wooden spoon, mix together the butter, brown sugar, and granulated sugar until creamy and well blended.
In a medium bowl, combine the flour, cinnamon, baking powder, and salt. Whisk gently to blend. Gradually mix into the butter mixture until just blended. Stir in the walnuts. Loosely pack the mixture into a bowl or a heavy-duty plastic food storage bag. Freeze until very firm, at least 4 hours or as long as 1 month.
Baking Day: Preheat oven to 350º. Grease a 2 1/2 to 3-quart shallow baking dish. Rinse rhubarb stalks under cold running water and discard any leaves. Cut stalks crosswise into pieces 1/2- to 3/4-inch thick. (You will have 9 to 10 cups.)
In a large bowl, mix together the sugar, flour, salt, and orange zest. Stir in orange juice. Add rhubarb, tossing to coat with sugar mixture. Scrape into the prepared dish.
Use a large knife to chop the frozen topping; then scatter the chunks and bits over the fruit. Bake until the topping is golden and the rhubarb is tender and bubbly-hot, 45 to 55 minutes. Let cool on a wire rack. Serve slightly warm, at room temperature, or lightly chilled.