The increase, which was attributed in part to increased promotional investment, was "particularly significant when compared to the wider cake market, which has remained flat", said the firm.
Sales of bread and free-from products were far stronger, achieving organic growth of 12.3% year-on-year over the 17-week period, driven by the continued success of the Genius fresh gluten-free range.
Group sales were up 4.9% compared with the corresponding period last year on a like-for-like basis, while operating margins had remained broadly unchanged despite increases in commodity prices, said chief executive John Duffy.
"We are pleased with the reported update and, remembering the remaining tough economic conditions, I am happy with the group’s progress so far this year.
"Finsbury remains a competitive player in its marketplace with a loyal and diversified customer base. We will remain adaptive to changes in market and customer demand by utilising our highly skilled, innovative and flexible production capability.”