The main sentence is "The topic is' The Art of Eating Spaghetti'". As a relative adverb, "on which" is equivalent to "where", which leads to the attributive clause modifying the antecedent "topic".

Topic → subject, on it → relative adverb, my eyes stopped → definite subordinate, yes → predicate, the art of eating spaghetti → object.

All relative adverbs can be converted into the form of "preposition +which", and the choice of prepositions should be based on the meaning of clauses. "My eyes stay at …" → "My eyes stay at …"