Coulis is a French term for a sauce made from puréed fruits.
You can use, thawed, frozen fruit in the winter. Just drain off some of the juice before using the berries.
3 cups raspberries
1/4-1/2 cup sugar
freshly squeezed lemon juice
Put the berries in the food processor or blender) with a 1/4 cup sugar to start. Blend until you have a liquid. Taste and season with lemon and more sugar as necessary.
Strain the sauce through a fine sieve into a bowl to eliminate any seeds.
Put sauce in a sealed container and refrigerate. It should keep for about 3 days.
If you are using this as a plate garnish and need it a little thicker, cook on the stove. Put the sugar and berries in a pot and cook down, simmering for about 15 minutes until some of the juice is reduced and the mixture is thickened. Strain and cool.