A million years ago, or a few months, one of those, I decided to finally make some apple butter. I had a bunch of applesauce in the freezer that was okay but not great, and wanted to make way for a new season's apples (and hopefully a better batch of sauce) but I was also sick of paying too much in the store for something that proudly boasted two kinds of corn syrup in its ingredients list.

I had no cider and no apple juice on hand, so I looked up some tips online for making apple butter with applesauce only and found a few ideas. So I'm going to share what I ended up doing, because it turned out great!
First off, because my BIG slow cooker went to live in soap making land long ago, all I have for actual cooking is this 4.5 quart one.
Applesauce frozen in 18 oz increments creates little bricks that only comically fit into my medium crock pot. Rather than thawing them, I just shoved in as many of the sauce bricks as I could and added the rest (thawed by then) the next morning after the first round had reduced.

So without further ado, here is what I did.
I had on hand 4.5 quarts of homemade applesauce (8 18oz containers in the freezer). Whatever amount you start with should cook down to half its original volume, so I ended up with about 4.5 pints of apple butter.
Also, I make our applesauce with only a dash of cinnamon and about a 1/4 cup of sugar (if any) per huge batch, so if you are using sweetened applesauce to start, you may want to taste test before you add the amount of sugar I am about to suggest.
Okay, so once your crock is full of applesauce just itching to get going (and again, these amounts are for a batch made from 4.5 quarts of applesauce; if making different batch size, please adjust accordingly!), you can add 2 tsp ground cinnamon, 1/2 tsp ground cloves, 1/4 tsp ground allspice, and one cup sugar.
Stir well, set slow cooker to low, and prepare for the long haul. (note: I left the lid on mine to start so it would help thaw the frozen applesauce. Once it had thawed, I placed the lid slightly askew so it could vent and facilitate the reducing process but still keep any splattering down to a minimum.)
Because my crock pot is pretty new, it heats very evenly and doesn't have any hot spots yet. Still, I did scrape the sides and stir mine down every few hours before I went to bed just to incorporate the edges into the main mixture. I kept mine on low overnight, but again, use your judgement. If you have an overzealous cooker, turn even lower or do not leave overnight.
After about 13 hours total on low, my first round of sauce had reduced enough for me to add the remaining applesauce and the rest of the sugar and spices.
In went 2 more tsp ground cinnamon, another 1/2 tsp ground cloves, and one more cup of sugar.

Because it was morning, and because I was feeling especially feisty, I turned my crock up to high for a few hours to really get things going, but I also stirred more often.
Progress was made.

Throughout the day, it darkened and reduced more and more.

This is what the whole pot looked like by the evening of the second day: cooked down to half the original volume and nice and dark.

After a good stirring, I had a sample and found it to be delicious! The consistency was perfect with a vigorous stirring, but if yours doesn't come out as smooth as you like it, you can also put it through a food mill.
The flavor is very similar to any commercial brand you can buy in the store, but a little tangier and less cloying as it contains no corn syrup or other excessive sweeteners.

For storage, I chose freezing (my usual method of choice). My hat is off to all you devoted canners, but I just can't do it. I used small jars and other containers so we wouldn't have any go to waste in the fridge. Storage time/safety are up to you. Our containers, once thawed, have all been eaten within a week, so I haven't had to worry about it. Upon poking around online for storage time suggestions, I came across anything from "I dunno, a week? Two months?" to "Heck, I don't even have a refrigerator! Mold is medicine!" so you can understand if I feel safer leaving that part up to your judgement...
Anyway. If you try it, let me know please! I'd love to know if you're as happy with it as I am.
