Combine the strawberries, rhubarb, water, and cinnamon in a saucepan and bring to a gentle simmer over medium heat. You should hear a soft bubbling as the fruit begins to soften and release its juices.
Stir occasionally with a wooden spoon to prevent sticking and encourage even cooking. As the mixture simmers for about 10 minutes, the fruit will become tender and start breaking down.
Add the sugar to the saucepan, stirring to dissolve and balance the tartness of the rhubarb with a hint of sweetness.
Continue simmering for another 5 to 10 minutes, mashing the fruit with the back of the spoon or a potato masher until it reaches your desired chunky or smooth consistency.
Once the mixture has thickened and the fruit is fully broken down with small bits remaining, remove the saucepan from heat. The applesauce should look jam-like with some visible pieces of rhubarb and strawberries.
Let the applesauce cool slightly before transferring it to a jar or bowl. Serve warm or chilled, enjoying its rustic texture and vibrant flavors.
