In a mixing bowl, combine all-purpose flour and white sugar. Cut in the unsalted butter until the mixture resembles coarse crumbs. Press firmly into a parchment-lined 9x9 baking dish and freeze for 15 minutes.

Preheat oven to 350°F (175°C). Bake crust for 10-15 minutes or until lightly golden. Avoid over-baking.

Mash fresh raspberries in a bowl. In another mixing bowl, whisk together eggs, granulated sugar, flour, lemon juice, and lemon zest until smooth. Fold in mashed raspberries.

Pour raspberry lemon filling over the warm crust and spread evenly with a spatula.

Bake for 25-30 minutes until filling is set around edges with a slight jiggle in the center.

Let bars cool at room temperature for about an hour, then refrigerate for at least 1 hour.

Dust with powdered sugar and garnish with fresh raspberries if desired. Cut into squares and serve.