1) Peel and slice meat off of mangoes. Add to food processor along with raspberries and process until desired consistency. You can also mash the fruit by hand, if desired. Add sugar.
2) Pour mixture into a medium sized saucepan and bring to a boil over medium heat. Reduce heat to simmer and simmer for about 5 minutes then bring back to a boil. Mix together lemon juice and cornstarch and add to pan, cook until thick. Store in airtight container in fridge for up to a week and a half.
Source of recipe: Needed to use up some mangoes, so I came up with this.