Position your oven rack in the bottom third of the oven and preheat the oven to 200 degrees. Line 2 large baking sheets with aluminum foil.
Using a small saucer or the rim of a large glass, trace 3 (4" diameter) circles onto the foil on each baking sheet using a food-safe, waterproof marker or pencil. Lightly butter the foil. Set the baking sheets aside.
In the bowl of a standing electric mixer, beat the egg whites and cream of tartar on medium speed until foamy. Carefully begin adding the superfine sugar, one tablespoon at a time, and increase the speed to medium-high. Continue to beat until the egg whites are stiff and glossy, about 7 minutes. Turn the mixer off and, using a spatula, transfer the meringue to a pastry bag fitted with a 1/2 inch plain tip.
Using the traced circles on the foil as guides, carefully pipe concentric circles of the meringue onto the buttered foil so that the circles are completely filled with the meringue. Pipe a second and then a third ring of meringue around the top outermost ring of each circle to form a shallow cup space. Place 1 tbsp of the confectioner's sugar in a fine-mesh sieve and shake the sugar evenly over the tops of the meringues.
Bake the meringues 1 1/2 to 2 hours, until crisp. They will not color. Turn the ove off and leave the meringues in the oven to cool and continue crsiping for at least 4 hours and up to overnight. They should feel very light. Remove the cool baking sheets from the oven and remove the meringue cups from the baking sheets by carefully peeling them off of the foil. Transfer to an airtight container, if storing. Meringues may be made up to several days in advance and kept in an airtight container until ready to serve.
Make the strawberry puree by combininb 2 cups of the strawberries with the 3 tbsp granulated sugar and the lemon juice in a blender or food processor and blend until very smooth, about 2 minutes. Strain the mixture through a fine-mesh sieve into a medium mixing bowl and discard the solids. Transfer the sauce to a nonreactive measuring cup or small glass bowl and chill until ready to serve.
If desired, place the cream in the bowl of an electric mixer and beat on medium-low until slightly thickened. Turn the mixer off and add the remaining 2 tbsp confectioners' sugar. Beat on low speed until the sugar is incorporated and then increase the speed to medium high. Continue to beat until stiff peaks form. Chill the whipped cream until ready to assemble the desserts.
When you are ready to serve, place each of the meringue cups on individual dessert plates and fill each with 2/3 cup of the remaining assorted berries. Top each with1/3 cup of whipped cream, if desired, and then spoon some of the strawberry sauce over the top.