Preheat the oven to 300° Fahrenheit and line a large baking sheet with parchment paper.
Make the pavlova. In a stand mixer, whisk the egg whites on medium speed until soft peaks start to form. This should take about 4-5 minutes. Then gradually pour in 1 1/4 cups granulated sugar and continue to whisk until stiff, shiny peaks form. This'll take another 2-3 minutes. Once you've got your stiff peaks (meaning when you lift the whisk out of the bowl, a peak forms and doesn't flop over), add in 1 tsp vanilla extract, 1 tsp lemon juice, and 1 tsp cornstarch and continue to whisk for another minute until everything is incorporated.
Transfer the pavlova base to your parchment paper lined baking sheet. I like to do this with a large spoon and then gently sweep the back of the spoon upwards around the entire pavlova to create a beautifully styled exterior. (You can totally skip ththe sweeping if you're going for a more rustic feel.) Then put the pavlova in the oven and decrease the temperature to 200° Fahrenheit. Cook for about 90 minutes, then turn the oven off and leave it alone for another 2 hours.
Pop a metal bowl for your stand mixer and its whisk attachment into the freezer so that they're nice and cold when you go to make your whipped cream. You'll want to leave them in there for at least 20 minutes before making the whipped cream.
Make the berry compote! To do this, put 1 cup of roughly chopped red berries (I used strawberries, raspberries and cherries) in a medium saucepan. Add 1 tbsp lemon juice and 1 tbsp granulated sugar and cook on medium heat for about 5 minutes, breaking up the berries with a large spoon as they cook. Set aside to cool for a few minutes, and then transfer to a food processor and blitz until smooth!
Make the whipped cream. To do this, pull your bowl and whisk out of the freezer and attach them to your mixer. Add 1 cup heavy whipping cream, 1/2 tsp vanilla extract and 1 tbsp granulated sugar to the bowl and whisk on high for about 1 minute, or until soft peaks form. Be careful not to overmix!
Now all that's left to do is assemble! Carefully peel your pavlova off the parchment paper and put it on your favorite platter or large plate. Add a generous serving of whipped cream to the top of it, followed by your berry compote. Finally, add as many fresh berries and pomegranate arils as you'd like and serve immediately!