In a medium saucepan, add raspberries, sugar, and water to a boil.
Turn onto a medium-low temperature, and simmer for 5 minutes, this will release the pectin in the fruit and thicken the sauce.
This recipe will give you 2 items when you cool it. 1 cup syrup, which I keep in a glass jar in the fridge to make drinks with and the thickened raspberry sauce.
Remove the saucepan from the stove and allow to cool 5 minutes.
Now you'll need 2 medium bowls and a fine mesh strainer.
Pour the raspberry mixture through the strainer so the syrup goes into the bowl.
Press the berries with the back of a spoon until all you see is the seeds remaining in the mesh strainer.
Then scrape the bottom of the strainer and place that thickened sauce into the other bowl, this is the filling.
Use the filling for cakes or cupcakes. Use immediately or place in the fridge to thicken.
Store in the fridge for up to one week