At the wedding ceremony the two sisters came to curry favor and the white dove pecked their eyes out. Two hollow spots were left like soup spoons.
The gore doesn't end with the amputating of feet parts. Oh no. As in the Grimm version, Sexton's Cinderella marries the Prince, and at the ceremony they come to "curry favor." (Basically this just means that they come begging for forgiveness, hoping to get in on some of Cinderella's newly found fortune.)
Of course, it wouldn't be a fairy tale if the bad guys got off the hook that easily. The white dove is having none of it and punishes them by pecking their eyes out. (Say it again: Ew. Also: Ouch!)
Then we are left with what is possibly the creepiest image in the whole poem, which is the stepsisters' eye sockets being "hollow spots" like "soup spoons."
Again with the crazy simile. Why soup spoons, of all things? There could be lots of possible explanations (which is both the fun and the frustration of poetry, of course). Maybe these remind us of Cinderella's kitchen duties as a maid, and so it's a final "take that!" to the girls. Or maybe these spoons, being empty (of both soup… and eyes), show us the starved nature of the sisters' characters. Or maybe you have other insights?