My recipe uses blueberries, but you should be able to substitute raspberries (or any other small berries):

2 cups blueberries (fresh, frozen, or canned)
1/3 to 1/2 cup sugar
1/4 cup water (if not using canned berries)
1 tsp. cornstarch
2 tsp. water

Place blueberries, sugar and 1/4 cup water (if needed) in a small saucepan. Heat, stirring, until the sugar dissolves. Dissolve the cornstarch in the 2 tsp. water. Add to the sauce and cook, stirring, til thickened.

Serve over cheesecake, ice cream, fresh fruit salad, pancakes, etc. Makes about 2-1/2 cups.