Put the yogurt, protein powder, salt and cinnamon in a small food processor and process until well combined. You might have to stop and scrape the sides once or twice to make sure you get all of the powder in there.
Add the frozen mango chunks and frozen raspberries (make sure the fruits are frozen solid) and process on pulse until the fruits are completely broken down and incorporated with the yogurt. You will have to stop and push the fruits back down into the blade's path a few times in the process.
This frozen yogurt is meant to be consumed immediately as it will become rock solid if stored in the freezer.
However, it can be placed in the freezer for up to 15 minutes to firm up a bit, if a firmer texture is desired.