Peel and cut butternut squash into 1-inch-thick rounds or the size of a hockey puck.
Mix together in a bowl the sugar, cinnamon, black pepper, lemon zest and salt. Mix with the butternut squash. Cover with plastic wrap placed in the refrigerator overnight.
Preheat the oven at 350 degrees F.
Take the plastic wrap off the squash and cover with foil. Bake for 45 minutes. Remove from the oven, flip the butternut squash, place the foil back on and cook for another 45 minutes.
Remove from the oven and let sit on the counter in its juices to get to room temperature. Once at room temperature, cover with plastic wrap and refrigerate for about 2 hours.
Whip the heavy cream until soft peaks form and add half of the tahini to the whipped cream. Reserve the other 2 tablespoons tahini to drizzle on top for garnish. Put the cooked butternut squash on a large platter and ladle over some of the cooking juices. Top with a few large dollops of whipped cream and garnish with drizzled tahini and the crushed pistachio nuts.