Preheat the oven to 400°F. Cut the squash in half lengthwise and scoop out the seeds. Cut the squash into 1/2-inch slices and transfer to a large baking sheet. Drizzle with olive oil and season with kosher salt and pepper. Toss the squash slices to coat them evenly with the oil and then spread out in a single layer.
Roast the squash for 30 to 35 minutes until tender. Pull the squash out after 20 minutes and flip the slices to encourage even browning.
To toast the hazelnuts, place in the oven on a baking sheet for 5 to 7 minutes until lightly toasted. To peel the hazelnuts, wrap the warm nuts in a tea towel and rub them together vigorously. This will remove most of the skins. Roughly chop the toasted hazelnuts and set aside.
To make the brown butter vinaigrette, have the apple cider vinegar and honey ready so that they can be added quickly to the brown butter. Melt the butter in a small skillet over medium heat. Cook for 4 to 5 minutes until the butter begins to turn a nutty brown colour. Swirl the pan while the butter is cooking to make sure it browns evenly.
When the butter is browned, immediately remove the skillet from the heat and carefully add the apple cider vinegar – it may spatter when it hits the hot butter. Swirl the butter and vinegar together. Add the honey and a big pinch of kosher salt and stir together until the honey is melted. Stir in the hazelnuts and dried cranberries.
To serve, transfer half of the squash slices to a serving platter. Drizzle half of the vinaigrette, hazelnuts, and cranberries over the squash. Repeat with the remaining squash and vinaigrette. Enjoy!