Pastry for single-crust pie (9 inches)
3 cups chopped fresh or frozen rhubarb
2 cups fresh raspberries
3/4 cup sugar
3 tablespoons all-purpose flour
1 teaspoon vanilla extract
1 egg, lightly beaten
1/4 teaspoon ground nutmeg

For the almond crumble:
2/3 cup whole oats, ground to a flour in a food processor (yielding 1/2 cup oat flour)
1/2 cup all-purpose flour
1/2 cup sugar
1/4 teaspoon ground cinnamon
1/2 teaspoon kosher salt or Less regular salt
3/4 cup unsalted whole almonds, coarsely ground in a food processor or chopped medium fine by hand
6 tablespoons unsalted butter, melted and cooled