Combine the hulled and quartered strawberries, granulated sugar, and lemon juice in a medium saucepan.
Cook over medium heat, stirring occasionally, until the strawberries begin to break down and release their juices, and the sugar has dissolved. This should take about 5-7 minutes.
Reduce the heat to low and simmer for another 8-10 minutes, stirring frequently, until the sauce has thickened to your desired consistency. Mash some of the strawberries with the back of your spoon if you prefer a smoother sauce.
If the sauce seems too thick, add a tablespoon or two of water to thin it out.
Remove from heat and let cool slightly before serving. The sauce will thicken further as it cools.
Notes
Store leftover strawberry sauce in an airtight container in the refrigerator for up to a week. Reheat gently if desired.