凉

The liàng reading is the causative twin of liáng: not 'X is cool', but 'let X become cool.' Always used as a transitive verb with a 把 construction or with a direct object - 凉一会儿 (let it cool for a while), 凉在桌上 (let it cool on the table). Don't mix the readings: 'this water is cool' is liáng, 'let this water cool' is liàng.

Cooks often write 晾 (the sun radical, 'air-dry') instead of 凉 in this sense - both are homophones with related meanings. Strictly, the food-cooling word is 凉 (ice radical, temperature-cooling); 晾 is for sun-drying laundry. In practice many native writers swap them.