Preheat the oven to 225 degrees F. Line a large baking sheet with parchment paper.
Process the thawed frozen raspberries with 2 tablespoons of the sugar in a food processor until smooth. Strain the puree through a fine-mesh sieve into a medium bowl, pressing on the solids with a rubber spatula; discard the solids.
Beat the 1/4 cup raspberry puree with the egg whites, cream of tartar and 1/4 teaspoon of salt in a stand mixer fitted with the whisk attachment at high speed until foamy, about 2 minutes. At medium speed, gradually beat in the remaining 3/4 cup sugar, then beat at high speed until stiff peaks form, 3 to 5 minutes. Beat in 1 to 2 drops of food coloring, if using, to reach your desired color.
Using a spoon, dollop 6 mounds of the meringue onto the prepared baking sheet, spacing them apart. Using the back of the spoon, spread the mounds into 4-inch rounds. Bake the meringues until crisp but still chewy on the inside, 1 hour to 1 hour 30 minutes. Transfer the baking sheet to a wire rack and let the meringues cool completely, about 1 hour.
In a clean and chilled bowl of a stand mixer fitted with a clean whisk attachment, beat the heavy cream until stiff peaks form; do not overbeat.
To serve, spoon some of the reserved raspberry puree on the cooled meringues, then top each with the whipped cream, more raspberry puree and the fresh raspberries