Wash, peel, and core the apples. Cut them into chunks or slices.
In a large saucepan, combine the apple chunks, water, and lemon juice (if using). Bring the mixture to a simmer over medium heat.
Reduce the heat to low and let the apples simmer, covered, for about 15-20 minutes, or until they are soft and easily mashable with a fork. Stir occasionally to prevent sticking.
Once the apples are soft, remove the saucepan from the heat. Use a potato masher or a fork to mash the apples to your desired consistency. For a smoother applesauce, you can use a blender or food processor to puree the cooked apples.
If the applesauce is too thick, you can stir in a little more water until you reach the desired consistency. Taste the applesauce and adjust the sweetness by adding sugar or sweetener if desired, although it's often unnecessary, especially if you're using sweet apples.
Allow the applesauce to cool completely before using it in your baking recipes. You can store it in an airtight container in the refrigerator for up to one week, or freeze it for longer storage.