Firstly, bring a large pan of water to a boil. And make sure that you put enough water in the pan to completely cover the can you're about to cook for hours.
Secondly, remove all the labels from the can of sweetened, condensed milk and then carefully submerge it into the boiling water using tongs or fork. Make sure you place the can on its side to avoid the bouncing of the can from boiling water.
Thirdly, cook the can for 2-3 hours, making sure the can is covered with water at all times. Also, add more boiling water if necessary to make sure that the can is always covered in water.
Note that you can have a more liquid caramel sauce after 1.5 hour of boiling, whereas 3 hours will give a brown and thick sauce.
After that, using a pair of tongs, a fork, or a spoon, carefully take the can out of the pan and place it onto a heatproof surface to cool.
Make sure the can has cooled to room temperature before you touch and open it, otherwise the homemade caramel will squirt out of the can like a fountain. Then, once the can is cooled, stir the thick sauce until smooth.
Finally, put the cooled dulce de leche in a tightly covered jar in the refrigerator for up to 3 weeks.
In case you want to enjoy it right away, just dip some fruits in it, spread it on cookies or bread, drizzle over cake or ice cream, or simply eat by the spoonful!