From Wiktionary, the free dictionary
nêm (“to season”) + nếm (“to taste”).
nêm nếm
- to season well
Ướp thịt nhớ nêm nếm cho kĩ, bỏ ít muối quá là lạt đó nghe.- Remember to use lots of seasonings when you marinate your meat, if you put too little salt, it would be just bland.