Put pears and water in a medium saucepan set over medium-high heat.
When the water starts to simmer, cover the pot and reduce the heat.
Cook for about 7-10 minutes, depending on the ripeness and size of the pear pieces. Riper fruit and smaller pieces cook down faster. When you can easily pierce the fruit with a fork, it is done. (Apples may take longer to cook and may need more water so they don’t dry out while cooking.)
Let the pears cool in the water, then puree in a blender or in the pot with an immersion blender.
The sauce keeps for 3-5 days in the fridge.
