Good for you if you have homemade sauerkraut on hand. I wish I did, but I do not, so I buy a jar.
1 onion, chopped
Drain the juice from the sauerkraut. Scald about 2 cups in a fry pan, drain again and press out all water. Chop very fine.
Add some oil to the fry pan and saute 1/2 cup of chopped onion.
Add to the sauerkraut and mix well.
This works best when you get as much water as possible out of the sauerkraut.