caramelize

US /ˈkɑːr.məl.aɪz/
UK /ˈkɑːr.məl.aɪz/
"caramelize" picture
1.

to heat sugar until it melts and turns into a thick, golden-brown syrup, used as a flavoring or coloring agent

:
You need to caramelize the sugar slowly to prevent it from burning.
The chef decided to caramelize the onions for a richer flavor.