Make the crust. Place the crust ingredients—flour, powdered sugar, and butter—in a blender or food processor. Process until a dough forms, about 30 seconds to a minute. Lightly grease the inside of a 9 to 10 inch wide, 1 inch high, tart pan with a little butter. Place the dough in the tart pan. Use your fingers to spread the dough and press it evenly all over the inside of the tart pan. (You can use a rolling pin to roll over the top of the tart pan to remove any excess dough and create an even top edge.) Place in the freezer and freeze for one hour or longer.
Pre-bake in a 350°F oven for 25 minutes. (It helps if before baking you line the crust with aluminum foil and fill with pie weights, such as dry beans; this will keep the tart crust from slumping.) Remove from the oven and let cool for 15 minutes.
Heat the oven again to 350F. Place the chopped walnuts in the crust in the tart pan and spread evenly over the bottom. Place the fresh or frozen raspberries on top of the walnuts and spread in an even layer.
Beat together the remaining filling ingredients—eggs, sugar, flour, baking powder, salt, vanilla—until smooth. Pour the egg mixture over the raspberries and walnuts in the crust.
Bake in the oven on the middle rack for 40 minutes, or until the top is nicely browned all over and the filling has set. When you remove the tart from the oven the center should still wiggle just a little. Take a sharp knife around the edge of the tart to separate it a little bit from the pan. This will make it easier to remove pieces once the tart has cooled. Let cool to room temperature to serve.
This salsa also doubles as a great meal when it is topped with shrimp and called “gazpacho.”
a little of each 