brunir

To turn or make brown — of skin in the sun, food while cooking, or metal with age. For sun-tanned skin specifically, bronzer is the far more idiomatic verb; brunir describes the broader color change (une peau brunie, du beurre qui brunit dans la poêle) more than the act of sunbathing itself.

• Le beurre brunit doucement dans la poêle. — The butter is slowly browning in the pan.
• Sa peau a bruni après une semaine à la plage. — Her skin turned brown after a week at the beach.
• Les feuilles brunissent avant de tomber. — The leaves turn brown before falling.

Learners often reach for brunir where bronzer is the natural choice for 'to tan' (je bronzais sur la plage, not je brunissais) — brunir is more at home describing food, wood, or metal changing color than a person sunbathing.

Often confused with bronzer.