puso (heart) + mamon (chiffon cake)
pusong mamón
a heart as soft as a sponge cake
pusong mamon
soft-hearted
Ito ay tambalang salita.
This is a compound word.
Mamón is the classic Filipino sponge cake. To have a “soft” heart means to have a sensitive nature, in the sense of being kind, sympathetic and merciful.
Philippine bakeshop chain Goldilocks came out with an actual heart-shaped mamon a few years back.

Albert Martinez and Eric Quizon starred in the 1998 romantic comedy film titled Pusong Mamon. It was directed by Joel Lamangan.
MGA KAHULUGAN SA TAGALOG
pusong-mamon: maawain; mahabagin
Thanks, I’m an American living in Cebu, trying to learn the language!