、。
When it comes to cooking, you're no match for Mary.
Literal
Cooking [quotative-と] say matter [conditional-になれば], you [topic-は] Mary [to-には] can't-match.
~ということになれば is a somewhat formal conditional meaning 'if it comes to the matter of X.' にはかなわない (can't match) uses には to mark the person being compared against. 君 is a casual second-person pronoun typically used by male speakers toward equals or juniors.