2 pounds rhubarb stalks (about 10), ends trimmed and stringy bits removed, cut crosswise into slices about 1/2 inch thick
1 cup packed dark brown sugar, divided
1 pound strawberries, hulled and cut into slices about 1/2 inch thick
2 tablespoons cornstarch
1 teaspoon fresh lemon juice
1 teaspoon almond extract
1/2 cup (1 stick) unsalted butter, at room temperature
1 1/2 cups packed light brown sugar
1 1/2 cups all-purpose flour
1 1/4 cups old-fashioned rolled oats
3/4 cup slivered almonds
1 1/2 teaspoons ground cinnamon
3/4 teaspoon kosher salt
1. Preheat oven to 375º. In a medium bowl, combine the rhubarb with 1/2 cup of the dark brown sugar; set aside. In a large bowl, combine the strawberries with the remaining 1/2 cup dark brown sugar; set aside.
2. After about 10 minutes, drain and discard any rhubarb juice that has accumulated in the bowl, and add the rhubarb to the strawberries. Add the cornstarch, lemon juice, and almond extract to the fruit, and stir gently until thoroughly mixed. Transfer the fruit mixture to a 9-by-13-inch baking dish and spread in an even layer. In another bowl, combine the butter, light brown sugar, flour, oats, almonds, cinnamon, and salt. Using your fingers or a pastry cutter, toss until large (2-inch) clumps of dough form. Evenly distribute the clumps of dough on top of the fruit mixture. Bake until the topping is golden brown and the juices are bubbling, 40 to 45 minutes. Let rest for 15 minutes, then cut into squares and serve.