Place the raw cashews in a bowl and fill with water, making sure the cashews are completely submerged. Soak at least 1 hour, up to 12 (note: you can prepare the crust while the cashews are soaking). Drain the water from the cashews.
Transfer cashews to a food processor or blender along with the remaining ingredients for the filling. Blend on high until completely smooth (this may require a minute or so).
Add all ingredients to a food processor and process until thick and cookie dough-like. You will need to stop the food processor a couple of times to scrape the sides with w rubber spatula to help the process along.
Press the crust firmly into a parchment-lined 8" x 8" pan, forming an even layer. Refrigerate crust until ready to use.
Pour the lemon filling into the pan with the crust. Smooth into an even layer, cover with plastic wrap, and freeze at least 2 hours. When ready to serve, thaw the bars at room temperature (or transfer to the refrigerator to allow them to thaw completely).
Release the bars from the pan by pulling on the parchment paper, and transfer to a cutting board. Use a sharp knife to cut lemon bars into desired sizes, and serve.
*You can soak the cashews for up to 12 hours if you'd like.
**You can replace the walnuts with cashews, almonds, or pecans