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

In a medium-sized mixing bowl, mix the all-purpose flour, granulated sugar, and salt until well combined.

Melt the unsalted butter and let it cool slightly. Add it to the dry mixture along with the egg and vanilla extract. Stir until just combined.

Pour the thick batter into the prepared baking dish and spread it evenly across the bottom.

In a separate bowl, mash the fresh raspberries, then mix in the fresh lemon juice and lemon zest.

Dollop spoonfuls of the raspberry mixture over the batter and gently swirl with a knife or toothpick.

Bake the bars in the preheated oven for 25-30 minutes until the edges are golden and a toothpick comes out clean.

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