Combine strawberries, sugar, cornstarch, salt, and lemon juice in a medium-sized saucepan.
Cook over medium/low heat until berries release their juices (about 5 minutes or so, mixture should be very liquidy).
Bring mixture to a boil and boil for one minute, stirring constantly.
Reduce heat to low and simmer until thickened, about 5 minutes (keep in mind sauce will continue to thicken after cooling).
Remove from heat and stir in vanilla extract, if using.
¹You can omit the cornstarch for a looser, less thick strawberry sauce. Keep in mind the sauce will need to cook much longer to reach a consistency that isn't too runny (about 15 minutes or longer).
²Optional. You can leave it out for a stronger, fresh strawberry taste, but I love the flavor the vanilla extract adds!