Ingredients :

• Red onions — Choose them firm, with dry skin that cracks under your fingers — avoid those that have started to soften on the surface. Roscoff or Toulouges onions are wonderful if you can find them, but classic supermarket ones work perfectly fine.
• Olive oil — A basic extra virgin is more than enough. No need for competition-grade oil for medium-heat cooking. Just avoid overly bitter oils that might weigh down the result.
• Salt — A pinch right at the start. It draws the moisture out of the onion and speeds up caramelization. Sea salt or fleur de sel is preferred.
• Lemon juice or balsamic vinegar — Optional on paper, essential in practice. Lemon brings a bright freshness that cuts through the sweetness. Balsamic gives a rounder, more velvety note. Try both on two different batches, you’ll see.