Combine walnuts, coconut sugar, 2 tablespoons coconut oil, and 1 tablespoon honey in the bowl of a food processor; pulse until fine, moist crumbs form, about 3 minutes. Press the crust mixture into the bottom of a 9-inch square baking dish.
Place cashews, lime juice, 1/2 cup honey, 5 tablespoons coconut oil, 1 tablespoon lime zest, and salt in a blender. Blend together until very smooth, about 4 minutes. Pour filling mixture over prepared crust.
Refrigerate until set, at least 20 minutes. Top with 1/2 teaspoon lime zest before serving.