For the Crust:

1. Preheat the oven to 350°F and butter an 8 x 8-in baking dish. Line with parchment paper, letting the parchment hang over two of the sides of the baking dish. Spray parchment with cooking spray.
2. Cream the butter and sugar together in the bowl of a mixer until smooth and fluffy. Add the flour, salt, and lime zest and mix until combined. Press the dough into the prepared pan. Bake for 10 minutes, or until it just starts to lightly brown around the edges.

For the Filling:

1. While the crust bakes, puree roughly 1 cup of fresh or defrosted frozen raspberries in a blender or food processor until smooth. Strain through a fine-mesh sieve and discard the seeds. Measure out ½ cup of the puree and add it to a mixing bowl.
2. Whisk in the flour, sugar, lime juice and zest, salt, and eggs. Stir until well combined. Pour the mixture over the crust and return the pan to the oven for 20-25 minutes, or until the filling is just set. Allow to cool to room temperature and then transfer to the refrigerator for at least 2 hours before slicing and serving.
3. Dust with powdered sugar and garnish with the fresh raspberries, if desired, before serving.