Slice the onions in thin long slices.

Add 2 tablespoons of oil in a large good quality iron skillet or pan and add the onions, mix well with the oil.

Cook in low to medium heat for 3 to 5 minutes until the onions begin to wilt.

Add salt, stir well to combine with the onions. Continue cooking the onions in medium low heat for another 10 to 15 minutes.

Stir in between to make sure the onions are not burning at the bottom of the pan and also the stirring will help the onions to caramelize evenly on all sides.

At this point, we are about half way through cooking the onions and the onions should have started browning although it's only a light brown color at this point.

Add lemon juice and if you are using sugar, add that too, mix well to combine with the onions.

Continue cooking the onions for another 8 to 10 minutes.

Stir well, increase the heat to medium and add the remaining oil (2 tablespoons of oil is remaining as we only used 2 tablespoons in the beginning).

Once the oil is added, stir well and cook the onions in medium heat for another few more minutes until onions are caramelized to your preference!

If you want only lightly caramelized onions, you can stop cooking once it has reached that stage.

If you want darker golden brown or intense dark brown color for your caramelized onions, you will need to cook for more time in medium low heat until the desired color is reached.

Always, make sure to adjust the heat as needed between medium and medium low to avoid the pan getting too hot which may cause the onions to burn. If the onions burn, that can cause bitter taste, so make sure to adjust the heat as needed.

In case the pan gets too hot in between and the onions start sticking, you can reduce the heat to low and cook while you stir the pan so the pan will cool down and the onions won't stick to the pan.

If anytime the onions stick, you may also add a splash of water and mix well if necessary to avoid the onions from burning.