Onion Skins Dyed Easter Eggs

This is an old recipe for dying eggs but
I just learned about it so it's new to me.
There's no food coloring involved in this.

Ingredients:
12 white large eggs
3 fresh red onions
3 fresh yellow onions
3 teaspoons red wine vinegar
1 teaspoon salt
aluminum foil to wrap eggs
4 cups cold water

Directions:
Cut top and bottoms off off the onions and
then remove the peels from the onions.
Set aside peeled onions for another use.
Chop peels in a food processor with salt.
Place red wine vinegar in a small bowl,
dip one egg at a time in the vinegar
and then coat with chopped onion peels.
Wrap up each egg in aluminum foil.
Place wrapped eggs in a sauce pan
and cover eggs with cold water.
Bring to a boil on high heat then
remove from heat and let sit for
about 20 minutes to color the eggs.
Remove eggs from water and unwrap foil.