Preheat oven to 250°F. Line two half sheets with baking paper.
In a stand mixer, whisk whites to soft peaks on medium speed. Still whisking, add the sugar one spoonful at a time. Once all the sugar is added, continue whisking at medium speed for 15 minutes. Test the meringue by lifting the whisk: it should be glossy, stiff and all the sugar should be dissolved. If you can feel sugar granules between your fingers, whisk for another 5 minutes, then check again. Combine vinegar and cornstarch in a small bowl. Whisk approx ½ cup meringue into vinegar and cornstarch mixture. Return this mixture to the rest of the meringue, then whisk for 30 seconds to combine.
Dab a small amount of meringue under the corners of baking paper so that it sticks to the baking sheet. Spoon 8 even mounds of meringue across the two sheets. Use a spoon to shape the pavlovas into circles, then form a well in the centre of each. Bake pavlovas at 250°F for 10 minutes, then reduce heat to 210°F and bake for another 40 minutes. Do not open the oven for any reason. Turn off the oven and let the pavlovas cool with the door closed for at least 1 hour.
To serve, fill each pavlova with whipped cream, then top with the blood orange segments and zest. Drizzle generously with Olive Oil and Balsamic Vinegar, then finish with a touch of sea salt.