Preheat your oven to 350°F (175°C). Line an 8x8-inch baking pan with aluminum foil, leaving some overhang for easy removal. Lightly spray with cooking spray.

Melt 1/2 cup of butter in a microwave-safe bowl for about 1 minute until fully liquefied. Let cool slightly.

Whisk the melted butter with granulated sugar, light brown sugar, and vanilla extract until smooth and creamy.

Stir in flour, rolled oats, and a pinch of salt until combined. Reserve 1 heaping cup of this mixture for topping.

Press the remaining mixture into the bottom of the prepared baking pan to create an even crust.

Spread 1 cup of raspberry preserves evenly over the crust, about 1/8 to 1/4 inch thick.

Sprinkle the reserved crumble mixture over the raspberry layer, creating a topping with varied textures.

Bake your bars for about 30 minutes until the edges are set and golden. Cool in the pan for at least 2 hours.