In a large pot, place the sweetened condensed milk can on its side and fill the pot with water until it reaches a level of about 2 1/2 to 3 inches above the can.
Set the stove to high and bring the water to a boil then reduce the heat setting to low and simmer for approximately 2 1/2 hours for a light amber caramel or 3 1/2 hours for a darker brown caramel. Make sure to check the water level of the pot every 20 minutes to ensure that the water level remains above the can. To top up the water, add boiling water into the pot as needed.
Carefully drain the water in the pot and remove the can with protective oven mitts or by using a tong.
Place the can onto a cooling pad or wire rack and cool to room temperature about 1 1/2 hour. Caution, do not open the can while it’s hot, it is under pressure and can cause the hot caramel to splash uncontrollably.
Once dulce de leche is completely cooled, transfer the caramel to an airtight container or mason jar and keep it refrigerated until ready to enjoy.