Preheat oven to 350°. Make filling: In a large bowl, combine granulated sugar, tapioca, and cornstarch. Stir in vanilla, then very gently stir in pluots and raspberries. Let stand 15 to 20 minutes, stirring occasionally, for tapioca to begin to soften. Transfer to a shallow 2 1/2- to 3 1/2-qt. baking dish, such as a 9- by 13-in. one.
Meanwhile, make streusel: In a large bowl, combine flour, brown sugar, coconut, sesame seeds, pumpkin seeds, almonds, and salt. Stir in vanilla and lemon zest. With your fingers, squeeze and rub butter into seed mixture until butter is completely blended and coarse lumps form. Scatter streusel over filling.
Bake until streusel is deep golden brown in center and filling starts to bubble in center, about 50 minutes. Let cool on a rack at least 1 hour.