First, make the raspberry sauce by blending the raspberries and sugar together. Sieve out the seeds for a more finished look. Set aside.
Preheat the oven to 400F.
In a very clean large ceramic, glass or metal bowl, beat the eggs whites until soft and foamy. As you continue to beat the egg whites, add in the sugar one tablespoon at a time. Beat until well incorporated after each spoonful. Add in the cream of tartar with the final spoon of sugar. Keep beating until you get a glossy mixture that doesn’t budge when you tilt the bowl.
Scoop the meringue into 6 rounds onto a baking sheet covered with parchment paper. Do not overstyle them, as they could deflate.
Gently drizzle some raspberry sauce onto each. Use a toothpick to swirl it into each pavlova. Again, try not to over-handle.
Before placing the pavlovas in the oven, reduce the temperature to 250F. Bake on the lower shelf for 70-80 minutes, until they are ivory (not browned). Resist the urge to open the oven door. Turn the heat off and let the pavlovas cool in the oven with the door propped oven with a wooden spoon. Let cool inside the oven for at least an hour or up to overnight. Taking them out too soon can result in them cracking and/or deflating.
Once cooled, remove from the oven and decorate with more raspberry sauce, fresh raspberries and chopped pistachios.