Preheat the oven to 400 degrees F (200 degrees C).
Cut the squash Butternut Squash (2 pound) in half lengthwise and scoop out the seeds.
Rub with Olive Oil (to taste) and Sea Salt (to taste) and arrange cut side down on a parchment lined baking sheet
Roast in the oven for 45 minutes, or until a fork easily slides in and out of the non-hallow half.
When cool enough to touch, scoop out the squash flesh and reserve in a bowl.
Add Garlic (1 clove), Mayonnaise (3 tablespoon), Gruyère Cheese (3/4 cup), Cayenne Pepper (1/4 teaspoon), and Fresh Parsley (1 tablespoon) to the squash flesh. Mix well. Taste for seasoning and add more salt as necessary.
Transfer to an oven safe ramekin or casserole and top with the remaining Gruyère Cheese (1/4 cup) and Pistachios (1/3 cup).
Bake until the cheese is melted (be careful not to burn the nuts), about 10 minutes.
Serve immediately with gluten-free crackers or baguette rounds.