Preheat your oven to 350°F (175°C). Grease an 8x8-inch baking dish or line it with parchment paper for easy removal.
In a medium bowl, combine the raspberries, 1/2 cup of sugar, lemon juice, and vanilla extract. Gently toss to coat the raspberries and set aside to marinate for about 10 minutes.
In another bowl, mix together the flour, rolled oats, remaining 1/2 cup of sugar, melted butter, cinnamon, and salt until crumbly.
Spread half of the crumble mixture evenly in the bottom of the prepared baking dish, pressing it down lightly.
Pour the raspberry mixture over the crumble base, spreading it evenly.
Sprinkle the remaining crumble mixture on top of the raspberries, covering them completely.
Bake in the preheated oven for 30-35 minutes or until the top is golden brown and the raspberries are bubbling.
Allow to cool for at least 15 minutes before serving. This will help the crumble set up a bit more.