"Casta" in Italian is pronounciated like /'Kasta/, as you see it written. In Italian language the letter "C" is pronounciated always as /k/ when is before vowals "a","u" and "o"( as in the Italian words "caro"=dear, "casa"= house, "colore"=colour," cucina"= kitchen).. Hope that is of help.. Have a great time!