Rare loanword from French 'chou rouge'. In everyday Japanese, 赤キャベツ (あかキャベツ) or 紫キャベツ (むらさきキャベツ) is more common.
from French chou rouge
See also: 赤キャベツ
In French cookbooks it's written as 'シュールージュ', but normally we say 赤キャベツ.
Variant with interpunct, reflecting the French phrase boundary.
From French 'chou rouge' (red cabbage).