Preheat oven to 350 degrees Fahrenheit. Fill a large roasting pan with 1/2 inch of water.

Place squash, cut side down, into the roasting pan. Cover tightly and cook until fork tender, about one and a half hours. Transfer to a baking sheet lined with a cooling rack. While still warm, remove seeds and peel. Alternatively, peel butternut squash before roasting.

Turn the broiler to high and set an oven rack closest to the heat source. Brush squash with onion caramel (recipe follows) and broil until golden, about two minutes. Brush again with onion caramel and continue to broil until just beginning to char. Lightly season with salt before serving.

Using a juicer, juice the onions, then strain through a fine-mesh strainer. Alternatively, purée onions in a blender or food processor and force the purée through a strainer. You should have about one and a half cups of juice, but it’s okay if there’s more because the liquid will evaporate.

Transfer juice to a two-quart saucepan and have a thermometer on hand. Add sugar and bring to a simmer over medium-low heat, stirring occasionally until sugar is dissolved. Simmer, stirring, until temperature reaches 240 degrees Fahrenheit, then remove from heat and let rest for one minute.

Add butter, one piece at a time, whisking until it’s incorporated before adding the next cube. Slowly whisk in cream and salt until fully incorporated. Store in an airtight container in the fridge for up to one month.