In a medium saucepan over medium-high heat, bring raspberries and 1/2 cup sugar to a boil. Reduce heat and simmer, stirring occasionally, until mixture starts to thicken, about 15 minutes.
Press mixture through a fine-mesh strainer, using a spatula to extract as much liquid as possible. Discard seeds and skins. Stir in 1 tbsp. lemon juice. Taste and add more sugar or lemon juice if you like. Serve coulis warm or at room temperature.
Note: Nutritional analysis is per 2-tbsp. serving.