Blend together cookie crumbs, melted unsalted butter, fine sea salt, and powdered sugar until resembling wet sand. Press into the bottom of an 8-inch cake pan lined with parchment paper. Bake at 350°F (175°C) for about 10 minutes, until lightly golden. Set aside to chill.

Lower oven to 325°F (160°C). In a clean food processor, combine cream cheese, granulated sugar, and fine sea salt, blending until smooth. Add vanilla extract and blend again. Incorporate pistachio butter and sour cream, mixing until well combined.

Add eggs one at a time, pulsing gently after each addition until just incorporated. If using lemon zest, add now and blend briefly.

Pour filling into the chilled crust, smoothing the top. Create a water bath and bake for approximately 50 minutes until edges are set. The center should jiggle slightly.

Once baking is complete, turn off the oven and crack the door, letting it cool for 30 minutes. Transfer to the counter to cool completely, then refrigerate for at least 8 hours.