Preheat the oven to 350ºF/180ºC.

Slice the onions in half. There's no need to peel them, unless you prefer to, at this point.

Place the fresh thyme into a large oven-safe dish or rimmed baking sheet (by placing it UNDER the onions, it won't burn). Then drizzle olive oil over it.

Spread the onion halves, cut-side down, and sprinkle the entire dish with a bit of salt.

Roast in the oven for 40-45 minutes, until the onions are tender and caramelized.

For quartered onions, peel them first if preferred, then roast for 30-35 minutes, flipping halfway.

For whole roasted onions, peel most of the layers of papery skin and cut off a bit from both ends. Drizzle with oil/seasonings and bake for 60-80 minutes, depending on size.