Preheat the oven to 275°F. Lightly grease a 9×13-inch baking pan.
For the meringue: In the bowl of a stand mixer fitted with the whisk attachment, or using a hand mixer, beat the egg whites, cream of tartar and salt on medium-high speed until foamy. With the mixer running, gradually add the bakers sugar, about 1 tablespoon at a time, and continue beating until stiff peaks form and the mixture is glossy. Spread the meringue evenly into the prepared pan.
Bake for 1 hour. Turn the oven off and leave the pan in the oven for 10–12 hours, or overnight, until the meringue is fully set and dry.
For the cherry berry topping: In a heavy-bottomed medium saucepan, combine the frozen dark sweet cherries, granulated sugar, cold water, lemon juice and cornstarch. Cook over medium-low heat, stirring frequently, until the mixture comes to a gentle simmer. Continue cooking for 10–20 minutes, until slightly thickened.
Pour the mixture into a medium bowl and cool at room temperature for 20–30 minutes. Stir in the sliced strawberries. Cover and refrigerate until fully chilled.
For the cream cheese filling: In the bowl of a stand mixer fitted with the whisk attachment, or using a hand mixer, beat together the cream cheese, powdered sugar and vanilla extract on medium speed until smooth. With the mixer running on low speed, slowly pour in the heavy cream. Scrape down the bottom and sides of the bowl. Increase the speed to medium-high and whip until light and fluffy, about 5–7 minutes.
Spread the cream cheese filling evenly over the cooled meringue. Cover and refrigerate for at least 4–6 hours, or up to overnight.
Cut into pieces and spoon the chilled cherry berry topping over each serving.