Core and peel the apples. Sure we can keep them but no one likes seeds and pieces of apple skins floating around in their freshly made sauce.
If a big batch of apple is made and we run the risk of the apples getting browned due to elongated exposure to air, squeeze some lemon juice and coat the apples with it.
Add water and the apples into a big enough cooking pot, place the lid on and bring it to boil. Add any optional ingredients if used.
Once the water is boiling and the apples start to come apart, reduce heat. If we plan to use apple sauce in the next couple of days, we can proceed to the next step but if we plan on canning it, cook it on medium to low heat for 15 minutes counting from boiling. Check out how to canning procedures works for more details.
Puree the apples with an immersion blender or whatever means possible. A fork or potato masher would also work.
Pour the apple sauce into cleaned jars for later use or let it cool a bit before using it in any recipes.