Preheat oven to 200°F. Line a baking sheet with parchment paper.
Pavlova: Using an electric mixer with the whisk attachment, whip together egg whites, salt and cream of tarter just until glossy peaks form. (Medium-high speed)
Whisk together 1 cup sugar and cornstarch in a separate bowl. Lower speed of mixer and gradually add sugar, about 3 Tbsp at a time. Beating just until stiff peaks form, don't overbeat. Add almond extract, mix on low just until combined.
Mound the meringue onto the center of the parchment lined pan, spreading into roughly a 9 inch circle. Leave the sides higher than center to form space to encase the filling.
Bake for 2 hours. Turn off oven,leaving meringue in the oven for another 2-3 hours or overnight.
Whipped Cream: Using an electric mixer, beat together cream, sugar and vanilla until stiff peaks form, don't overbeat. Spread into center of pavlova.
Toss sliced strawberries with 1 Tbsp sugar, stir and let sit for a few minutes to macerate..
Arrange, strawberries, blueberries and raspberries over cream.
Slice and serve immediately.