1. Preheat oven to 325° F. Using an electric mixer, beat the egg whites until they are thick and white. Slowly sprinkle in the 3/4 cup of sugar and cornstarch. Beat until stiff peaks form. Line a large baking sheet with parchment paper. Smear a teaspoon of batter on the back side of the parchment to hold it in place. Using a 3-inch bowl or biscuit cutter, draw 6 circles (2 inches apart) on the parchment paper.
2. Transfer the meringue mixture into a large piping bag fitted with a wide star tip. Pipe the meringue in a continuous spiral, starting from the outer edge of a circle and working inward. Add a second layer the same way. Repeat the process for the remaining circles and meringue.
3. Use a teaspoon to gently press down the center of each pavlova to create an indention for the curd and garnish.
4. Place in the oven. Turn the heat down to 225° F. Bake for 1 hour to 1 hour 30 minutes until pavlovas are dry to the touch. Turn off the oven, and let cool in the oven for 1 hour. Transfer to a wire rack to cool completely.
5. For the lemon curd, combine the juice and sugar in a small saucepan over medium heat. Whisk until sugar is dissolved. Add the butter, and whisk until melted. Break the eggs into a medium bowl. Whisk to combine. Slowly add small amounts of the hot juice mixture to the eggs. Continue to whisk while slowly pouring. Add the contents of the bowl back to the saucepan.
6. On low to medium heat, cook the curd for 5 to 7 minutes (whisking constantly) until it thickens enough to coat the back of a spoon. Turn off the heat. Pour the curd into a bowl. Let cool for 15 minutes. Stir again, and transfer to the refrigerator until completely cooled. Leftover curd can be stored in an airtight container in the fridge for up to 3 weeks.
7. To serve, spoon the lemon curd over the pavlovas. Garnish with peeled citrus slices and pistachios.

Per Serving (1): Calories: 430, Fat: 19 g (11 g Saturated Fat), Cholesterol: 165 mg, Sodium: 95 mg, Carbohydrates: 60 g, Fiber: 0 g, Protein: 7 g.