Here's how to do it. Really simple and easy.
Pour two cans of sweetened condensed milk (not evaporated milk) into a shallow baking dish. Add a pinch of salt and stir.
Set the pie plate within a larger pan, such as a roasting pan, and add hot water until it reaches halfway up the side of the pie plate.
Cover the pie plate snugly with aluminum foil and bake for 75 to 90 minutes. I usually just leave it for 90 minutes. (Check a few times during baking and add more water to the roasting pan as necessary).
Once the Dulce de Leche is nicely browned and caramelized, remove from the oven and let cool. Once cool, whisk until smooth.
Store in the refrigerator until ready to serve. Warm gently in a warm water bath or microwave oven before using.