You can make it by peeling and coring several apples. The tart ones work best. Then slice them in small pieces. Put them in a pan with a small amount of water and let them cook at a reasonably low temperature until they cook down. But if you are at the right temperature, they will start juicing up and making liquid of thier own.
Some people add a little salt or sugar.
We like to add a bit of cinnamon sugar. But it is not needed.