Preheat your oven to 275F. Line a cookie sheet with parchment paper. If you have a cardboard circle at least 10” wide, go ahead and place that over the parchment.
Beat your egg whites with the cream of tartar with a handheld mixer or in a stand mixer with whisk attachment until soft peak stage. Slowly stream in the sugar (while beating) and beat until very stiff and glossy. Fold in the cornstarch.
Dump the meringue into a tall stack about 8” wide. Swirl the center down to make a well using the back of a metal spoon.
Bake for about 1- ½ hrs. Turn the oven off and allow the pavlova to cool in the oven for 15 minutes. Remove from the oven to continue cooling for another 20 minutes.
Once cooled, fold half of your whipped cream into the lemon curd. Spoon into the center of the pavlova and top with swirls of remaining whipped cream. Serve immediately or freeze and serve as a frozen dessert.
LEMON CURD
Place a saucepot, ½ filled with water, on the heat and bring to a simmer.
In a medium-sized bowl, whisk together the eggs and sugar. Whisk in the juice. Set the bowl above the pot and reduce heat to low.
Stir the mixture over heat until a thick custard forms (this may take about 10 minutes).
Remove from heat and stir in the butter until smooth. Cool to set.