For the fruit:

1. Toss the fruit with the lemon juice and sugar in a large bowl.  Refrigerate until ready to use.

For the pavlova:

1. Move oven rack closest to the top.  Preheat the oven to 275 degrees.
2. Mix the sugar with the cornstarch in a medium bowl; set aside.
3. Using the whisk attachment of a clean and dry stand mixer, whisk the egg whites and cream of tartar at high speed for 8 to 10 minutes, until the egg whites hold their shape and the whisk leaves a path in the whites.  Do not over mix.
4. Switch to medium speed; add the sugar mixture tablespoon by tablespoon, waiting until each spoonful is incorporated before adding more.  The meringue should be firm and glossy.
5. Prepare a large baking sheet with parchment paper. Draw a 10-inch diameter circle onto the center of the parchment paper, then turn the paper over and place back onto the baking sheet and lightly coat with cooking spray.
6. Using a wooden spoon, heap the meringue onto the parchment paper-lined baking sheet keeping within the circle. Using the spoon, flatten the top and shape it into a round circle.
7. Place the baking sheet in the oven; bake at 275 degrees undisturbed for 45 minutes.  Rotate and bake for another 20 minutes.  The round should be crusty when (very gently) touched.  If not, bake for another 10 to 15 minutes.  Remove from oven and allow to cool.  Carefully remove from the parchment paper.

For the whipping cream:

1. In a stand mixer fitted with the whisk attachment, add the cream, powder sugar, and vanilla.  Start on low speed, then slowly turn the mixer up to high speed and continue mixing on high for 2 to 3 minutes until fluffy and the cream holds a soft peak when you pull the whisk out of the bowl.

Top the meringue with the whipped cream and fruit mixture.  Serve immediately.