Actually, ON the dead!
Aside from Sugar Skulls,
the traditional treat to eat today are Soul Cakes.
Made for All Saints' Day or All Souls' Day to celebrate the dead.
Each cake eaten represents a soul being freed from Purgatory.
They were given out to "soulers" (usually children) who went from door to door calling out words such as those in the song A Soalin' by Peter, Paul and Mary:
"Soal, a soal, a soal cake, please good missus a soul cake,
An apple, a pear, a plum, a cherry,
Any good thing to make us all merry,
One for Peter, two for Paul, three for Him who made us all."
A recipe for the cakes and iced pumpkin juice is located here!