Peel and slice the onions thinly.

Place your skillet over medium heat and add the butter and olive oil.

Once the butter has melted, add the sliced onions to the skillet.

Sprinkle the salt over the onions.

Cook the onions, stirring occasionally, for about 40 minutes.

If desired, sprinkle in the sugar after about 20 minutes.

After 40 minutes, the onions should be golden brown and soft.

Taste and adjust seasoning if needed, then remove the skillet from heat.