1. Peel, core and quarter all the apples and pears. 
2. Place the apples and pears into a large pot. Fill the pot with water. If you are making Kompot (apple and pear drink), then add all the water, filling the pot to the top. However, if you only want to make sauce, add enough water to only cover the fruit. 
3. Add the sugar, if you are using it. 
4. Bring the water to a boil, then reduce the heat to a simmer. Cook, covered for 20-30 minutes, depending on how big you cut the fruit and the variety of apples and pears you are using. The fruit should be tender and soft, almost starting to break down. 
5. Drain the liquid, pouring it through a fine mesh sieve, if you are going to use the liquid for Kompot. 
6. Mash the apples, using a potato masher if you want a more rustic texture or a food processor or blender if you want it to have a smooth texture. 
7. Add the lemon juice. You can also add vanilla extract and cinnamon, for flavoring the sauce.
8. Store the applesauce in the refrigerator for about a week. 

You can also preserve it by canning the applesauce in sterilized jars or freeze in airtight containers or freezer ziplock bags for about 6 months.