In a saucepan over medium heat, add strawberries, sugar, lemon juice, and cornstarch. Stir to combine. If your strawberries are not very juicy, add 1-2 tablespoons of water as needed.
Bring to a boil. Reduce heat to medium-low and cook until mixture has thickened and looks glossy (this could take up to 6-8 minutes). Remove from heat and allow to cool.
Store topping in the refrigerator until ready to serve.
Notes
Add 1-2 tablespoons of water if strawberries are not very juicy for the right consistency.