01 - Preheat the oven to 350°F.
02 - In a medium bowl, combine raspberries, granulated sugar, lemon juice, and cornstarch. Toss gently to coat, then pour into a lightly greased baking dish (approximately 8x8 inches).
03 - In a food processor, pulse pistachios until coarsely chopped.
04 - In a separate bowl, combine chopped pistachios, flour, oats, brown sugar, and salt. Add cold butter and rub together with fingertips until the mixture resembles coarse crumbs.
05 - Sprinkle the crumble topping evenly over the raspberry mixture.
06 - Bake in the preheated oven for 30 minutes, or until the topping is golden and the fruit is bubbling.
07 - Let cool slightly before serving. Serve warm, optionally with a scoop of vanilla ice cream or whipped cream.