Every recipe that says caramelize onions in ten minutes is lying to you. What you get in ten minutes is browned, slightly bitter onions. Real caramelized onions, jammy and sweet and almost spreadable, take forty minutes or more. The good news is that almost all of that is hands-off.
Slice them evenly
Cut the onions root to tip into thin, even slices so they cook at the same rate. A couple of large onions cooks down to a surprisingly small pile, so do more than you think you need. They keep in the fridge for a week and freeze well.
Low and slow is the whole game
Melt a little butter or oil in a wide pan over medium-low heat. Add the onions and a pinch of salt, which pulls out moisture and speeds things along. Then mostly leave them be, stirring every few minutes.
- First they go soft and translucent.
- Then pale gold, then amber, then deep brown.
- If they start sticking or browning in spots, the heat is too high. Turn it down.
Deglaze when they stick
The brown film that builds on the bottom of the pan is pure flavor. When it starts to look dark, add a splash of water and scrape it up. It dissolves back into the onions. Repeat as needed. Resist the urge to rush. If you crank the heat to save time, you get scorched edges and raw centers. Done right, they are good on burgers, in soup, folded into eggs, or piled on toast with cheese.