Heat a pan in low fire. (It’s best to use a non-stick pan)
Add the sugar and let it caramelize. Do not stir until it caramelizes completely. Just swirl the pan.
Add the butter and let it melt.
Add the condensed milk. Cook while continuously stirring. You will notice the caramel will get hard but it’s okay it will melt later on.
After 5 minutes, add the egg yolk, salt, vanilla, and calamansi juice. Cook for another 5 minutes while continuously stirring to avoid burning of the mixture.
After 5 minutes, adjust to medium heat. Continue cooking for another 5 minutes while stirring faster. For a total of 15 minutes the yema spread is done. Turn off the heat and let it cool.
Prepare the container for the yema spread. Sterilize an empty glass jar into boiling water for 10 minutes. This process will make the shelf life of yema spread longer.
Transfer the yema spread to the sterilized jar and place the cap.
Serve with your favorite bread and enjoy your yema spread!