• Preheat the oven to 350°F. Line an 8-inch square baking pan with parchment paper, leaving overhang on two sides for easy removal.

Make Crust & Crumble

• In a large bowl, whisk together the melted butter and sugar until smooth and slightly lighter in color. Whisk in the sourdough discard and vanilla. Add the flour, oats, and salt, then fold until a thick, crumbly dough forms.
  1 cup (226 grams; 2 sticks) unsalted butter, ½ cup (100 grams) granulated sugar, ½ cup (100 grams) sourdough starter discard, 1 teaspoon vanilla extract, 2 cups (240 grams) all-purpose flour, 1 cup (80 grams) rolled oats, 1 teaspoon Diamond Crystal Kosher Salt
• Reserve 1 cup of the crumble and refrigerate it for the topping. Press the remaining mixture firmly into the prepared pan. Bake for 15–20 minutes, or until set. Set aside to cool slightly.

Make Raspberry Sauce

• In a small saucepan over medium-low heat, combine raspberries and sugar. Cook, stirring and gently crushing the berries, until they break down and become syrupy, about 10 minutes.
  2 cups (280 grams) fresh or frozen raspberries, ¼ cup (50 grams) granulated sugar
• In a small bowl, whisk together the lemon juice and cornstarch. Remove the raspberry mixture from heat and stir in the cornstarch slurry. Continue stirring until thickened. Set aside to cool.
  1 tablespoon lemon juice, 1 tablespoon cornstarch
Let the raspberry sauce cool before assembling so it doesn’t thin the cheesecake layer.

Make Cheesecake Filling

• In a medium bowl, beat the cream cheese and sugar until smooth. Add the egg and vanilla and mix until fully combined and creamy.
  8 ounces (226 grams) cream cheese, ¼ cup (50 grams) granulated sugar, 1 large egg, 1 teaspoon vanilla extract

Assemble and Bake

• Pour the cheesecake mixture over the partially baked crust and spread evenly. Spoon the raspberry sauce over the top and swirl gently with a knife or toothpick. Sprinkle the reserved crumble evenly over the top.
• Bake for 45–50 minutes, or until the top is golden and the center is just slightly jiggly.
• Cool completely in the pan, then refrigerate before slicing into 16 bars for clean cuts.