Preheat the oven to 350 degrees F (175 degrees C). Grease an 8×8-inch baking pan.
Stir melted butter, white sugar, and light brown sugar together. Stir in flour to form a crumbly mixture. Set 3/4 cup of the mixture aside for the topping. Add raspberry baking chips and salt to the remaining mixture.
Pour raspberry crumb mixture into the prepared pan, distributing it evenly. Use the back of a spoon to press the crumb mixture down into the pan to form a level crust. Spread lemon curd over the crust and top with the reserved crumbs.
Bake in the preheated oven for 35 to 40 minutes. Cool in the pan for 20 minutes, then refrigerate until bars are set, about 1 hour.
While the bars are cooling, make the raspberry sauce. Place raspberry preserves in a microwave-safe bowl and microwave on high until easily stirred with a spoon, about 40 seconds. Stir in raspberry liqueur and refrigerate until cool.
Cut bars into 9 pieces and drizzle with raspberry sauce.