Preheat your oven to 350°F (175°C) and line an 8-inch square baking pan with parchment paper.

In a mixing bowl, combine 1 cup of all-purpose flour, ¼ cup of powdered sugar, and a pinch of salt. Mix in ½ cup of melted unsalted butter until crumbly and press into the bottom of the prepared baking pan.

Bake the crust for 16-18 minutes until golden brown and firm.

Prepare the raspberry sauce by mashing 1 cup of raspberries with 1 tablespoon of sugar and1 tablespoon of cornstarch in a saucepan over medium heat until thickened, about 4-5 minutes. Set aside to cool.

Whisk together 1 cup of granulated sugar and 2 tablespoons of flour. Add 3 eggs, ½ cup of fresh lemon juice, the zest of 1 lemon, and 1 teaspoon of vanilla extract, mixing until smooth.

Pour the lemon filling over the warm crust and dot with raspberry sauce. Use a knife or toothpick to create swirls.

Bake the bars for 22-26 minutes until the edges are set and the center has a slight jiggle.

Cool at room temperature for 30 minutes, then refrigerate for at least 2 hours to set.

Dust with powdered sugar before serving and slice into squares.