Mix cornstarch with cold water. Stir until cornstarch is completely dissolved.

Put frozen raspberries into a saucepot over medium/low heat until berries are thawed and juicy.

Whisk in cornstarch/water mixture and increase heat to medium-high.

Continue to stir until the sauce boils and thickens. Reduce heat to medium and stir in sugar and lime juice. Stir until sugar has dissolved. Remove from the heat and cool. Serve warm, room temp or chilled.