Cynon is one of the first protagonists in the Mabinogion of Iarlles y Ffynnawn (Countess of the Spring). His name also appears in three poems in the Trioedd Ynys Prydein. Cynon's name probably represents a Cymric form of the proposed Brythonic proper name *Kunonos (great/divine hound). He is a hero in the early epic poem Y Gododdin and the collection of poems known as the Englynion y Beeddau (Stanzas of the Graves) also gives the location of Cynon's grave.
Originally Cynon was an historical figure, one of the Gwŷr y Gogledd (The Men of the North). As such he is named in Aneirin's battle poem, the Gododdin as on of the prominent heroes of the ill-fated expedition to Catraeth (Catterick) where it is stated that he was the 'son of Clydno of distant fame'. Either 300 or 363 men went on that expedition and in two opposing statements it seems that either there was but a single survior or that Cynon survived along with three others (of whom the poet Aneirin was one). I believe that this second statement was an additon by a later redactor of the tale made to fit in with the later Cymirc englynion y beddau (Stanzas of the Grave) and though at least three of these stanzas refers to Clydno, only one gives his grave site as being in Llan Badarn (which may well have been near Llyn Padarn in Arfon). However, this is a later tradition (and fits in with the practice of re-locating the heroes of the Old North to new Cymric locales). And it was this that led to the later naming of Cynon as one of the survivors of Catraeth which is not supported elsewhere in the Gododdin.
What seems likely is that Cynon, Clydno and Urien of Rheged (to whom Taliesin sings his praise poetry) were contemporaries and this probability sheds some light on the remaining fragments of Cynon lore. In the Mabinogion, though he is not named in the lists of heroes related in the tales of Culhwch ac Olwen and Breuddwyd Rhonabwy he is one of the first protagonists of the Mabinogion of Owein (also known as Iarlles y Ffynon [The Countess of the Spring]). Cynon son of Clydno, Cei son of Cymer and Owein son of Urien are relating tales of their exploits to Arthur and it is Cynon's turn to pay Cei for the meat he provided by relating a tale. He tells of his exploits in a distant land where he seeks the realm's greatest knight to do battle with him. He tarries a night in a magnificent castle and asks his host where he might encounter such a knight. He is directed to a glade where he encounters a black one-eyed, one-footed giant, the master of beasts (probably a late version of Cernunnos). Eventually the giant figure directs him down a forest path and to a clearing in a high plane that contains a spring with a stone block nearby and a silver bowl attached by it to a silver chain. Taking water from the spring and pouring it onto the stone will summon the black knight, protector of the spring. The knight and Cynon do battle but Cynon is defeated and his horse is taken. He makes his way back disgraced, and speaks of this no more. Hearing this, Owein son of Urien is determined to encounter the knight himself and defeat him. Thus begin his adventures.
In the Trioedd Ynys Prydein Cynon is mentioned three times. The first time in the Peniarth 50 variant of triad 33 where he and Dyfynnawl mab Mynedawc are named as the assassins of Urien mab Cynfarch (Urien Rheged) though this variant of the poem seems to have arisen from the redactor's desire to bring together all the wariors to whom the epithed Eiddyn (belonging to or originating from the Edinburgh region of modern Scotland) into one narrative rather than from any real tradition. Triad 71 names Cynon as the lover of Morfudd, daughter of Urien Rheged. Though this seems to be a tradition originating from the fourteenth century. Appending IV of the triads names Cynon as one of Arthur's three counsellor knights. The only other mention of Cynon comes from the genealogies contained in Bonedd y Seint (The lineages of the Saints) where Cynon is ascribed a sister who is named as either Creirwy (Peniarth 16 MSS) or Euronwy (Vidae Sanctorum Britanniae et Genealogiae).
If you would like to try the foods of the time of the ancient Celts, then why not have a look at the ancient recipes section of this site. For the foods of the time when some of these tales were written down, take a look at the Medieval recipes section of the site and, in particular, the recipes from The Forme of Cury.