Preheat your oven to 350°F (180°C) and line a baking dish or tray with a large sheet of foil.
Peel the onions. Trim the root end just enough that each onion stands upright on its own — but no more than that. Cut too deep and the onion falls apart as it bakes; you want it staying intact so it holds all that buttery broth inside.
Step 2 — Cut the cavity
With a small paring knife, cut a shallow cone-shaped well into the top center of each onion — like
