SALVETE OMNES, S.V.B.E.V.
Is there a you singular formal tense in Latin?
Every Romance language I have encountered shares the 3rd person singular (he, she, it) with you singular formal.
But I haven’t encountered such a thing in any of the Latin grammars yet.
MVLTAS GRATIAS!
Not in formal Latin, but I can’t speak for Vulgar Latin from which the Romance languages originate.
In Spanish, at least, “usted.” is a contraction of “your grace”, which is why it is in the third person. I can’t vouch for other languages. Perhaps a similar phrase existed in vulgar latin.