In a large pot or 3-quart saucepan, heat evaporated milk over medium-low heat. Add the sugar and lime rind.Once it breaks the boil, adjust the flame until it settles on a gentle boil, and simmer, stirring with a wooden spoon or spatula as necessary to prevent it from overboiling or burning.Once it starts thickening (30-40 mins), whisk vigorously until it has become so thick that it sticks to the spoon (similar consistency to peanut butter).
3. Mold
Discard the lime rind, spoon the mixture into the prepared mold, and smooth it out. Let it cool to room temperature.Remove from the mold and cut into six squares.
Notes
I did not have a mold the size of the traditional Dominican one, I improvised by covered a cardboard box of similar size with aluminum foil and spraying with oil. The size I used was 3"L x 4 ½"W x 2"H [6.75 cm L x 9.5 cm W x 4.5cm].