Preheat your oven to 350°F (175°C) and prepare an 8x8-inch baking dish by greasing or lining it.

In a medium mixing bowl, whisk together the all-purpose flour, granulated sugar, and salt. Add melted butter, egg, and vanilla, stirring until smooth.

Pour the batter into the prepared dish, spreading it evenly into the corners.

In a separate bowl, mash the raspberries with a fork, then add lemon juice and zest.

Drop spoonfuls of the raspberry mixture over the batter and swirl gently with a knife.

Bake for 25 to 30 minutes until edges are golden brown; a toothpick inserted should come out clean.

Allow the bars to cool in the pan for about 10 minutes, then transfer to a wire rack to cool completely. Dust with powdered sugar before serving.