- Place berries on a baking sheet and sprinkle with half of the sugar. Place 5–6 inches under a preheated broiler, and broil until well browned.
- Remove and set aside until cool.
- Combine cream, salt, and remaining sugar in a heavy saucepan over medium high heat. Add the raspberries, and boil until berries break easily.
- Remove from the heat and set aside until cool. Purée in a food processor or blender until smooth. Alternatively, use an immersion blender directly in the saucepan.
- Pour mixture back into saucepan, and place over medium high heat. Bring to a boil and cook until liquid has reduced by ⅔.
- Stir in butter and vanilla until smooth, then cool.
- Pour sauce over ice cream or fruit and serve.