Preheat the oven to 475 degrees F (245 degrees C).

Grease a 9x13 inch baking dish.

Season halibut with salt and ground black pepper.

Place halibut in the greased baking dish.

Combine green onions, mayonnaise, sour cream, and dill in a bowl.

Spread green onion mixture evenly over each halibut piece.

Bake in the preheated oven until fish is opaque and flakes easily with a fork, about 20 minutes.

Remove from the oven and let stand for 5 minutes before serving.