In a medium saucepan over medium heat, combine 2 cups raspberries, 1 cup granulated sugar, and 1 tablespoon lemon juice.

Bring the mixture to a gentle boil, stirring occasionally to help the raspberries break down.

Using a wooden spoon or spatula, gently mash the raspberries as they soften to release more juice.

Reduce heat to low and simmer for 10 minutes, stirring occasionally to thicken the sauce.

If you prefer a thicker sauce, whisk 1 tablespoon cornstarch with 2 tablespoons water in a small bowl and stir into the sauce during the last 2 minutes of cooking.

Optional: Strain the sauce through a fine-mesh strainer into a bowl to remove seeds and achieve a smooth texture.

Remove from heat and allow the sauce to cool slightly; it will thicken further as it cools.

Serve immediately drizzled over desserts or breakfasts, or store in an airtight container in the refrigerator for up to one week.