The Collaborative International Dictionary of English v.0.48:
Austerely \Aus*tere"ly\, adv. Severely; rigidly; sternly. [1913 Webster] A doctrine austerely logical. --Macaulay. [1913 Webster]WordNet (r) 3.0 (2006):
austerely adv 1: in an austere fashion; "the church was austerely simple"