Yes. For UK VAT purposes, Jaffa Cakes are treated as cakes, not chocolate-covered biscuits. In the 1991 tribunal case United Biscuits (LON/91/0160), the tribunal weighed factors such as sponge-cake ingredients and texture, and the fact that Jaffa Cakes harden when stale (like cake) rather than soften (like biscuits). It concluded they had enough cake characteristics to be accepted as cakes and therefore zero-rated.
HMRC still treats that case as the leading authority on the cake–biscuit borderline, and current HMRC food VAT guidance lists Jaffa cakes among zero-rated bakery items.
Source: HMRC internal manual VFOOD6260 — The borderline between cakes and biscuits (see also VAT Notice 701/14).