Preheat your oven to 350°F (175°C). Gather all your ingredients and equipment.

In a large mixing bowl, combine the butternut squash and apples. Gently toss them together until well mixed.

Sprinkle brown sugar, ground cinnamon, ground nutmeg, and salt over the squash and apple mixture. Stir gently to coat evenly.

Drizzle lemon juice over the mixture and toss everything together again.

Transfer the coated mixture into a greased 9x13 inch baking dish and spread it out evenly.

In a small bowl, mix melted unsalted butter with granola or oats. If desired, add chopped pecans or walnuts.

Evenly distribute the granola mixture over the butternut squash and apple layer.

Cover with aluminum foil and bake for 25 minutes.

After 25 minutes, remove the foil and continue baking for an additional 15-20 minutes until the squash is tender and the topping is golden brown.

Remove from the oven and let cool slightly before serving.