Heat a saucepan over low/medium heat.

Stir 2 cups of raspberries, sugar, lemon juice, 3 tablespoons water into pan and bring to a boil.

Let boil for 3-4 minutes, then add remaining 1 cup of raspberries. Stir.

Mix 4 tablespoons water and corn starch together. Add to raspberries and stir.

Continue cooking until sauce thickens.

Remove from heat and either serve warm over pancakes, french toast, etc., or cool and use for toppings on cheesecakes, crepes, etc.