The Collaborative International Dictionary of English v.0.48:

flavourer \flavourer\ n.
   same as flavoring. [Chiefly Brit.]

   Syn: flavorer, flavoring, flavouring, seasoner, seasoning.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

flavourer
    n 1: something added to food primarily for the savor it imparts
         [syn: flavorer, flavourer, flavoring, flavouring,
         seasoner, seasoning]