Preheat oven to 300ºF.

In a stand mixer with whisk attachment, beat egg whites on medium-high speed until frothy. While mixer is running, start adding 1 cup of the sugar, about a tablespoon at a time, until glossy, stiff peaks form. Spread this meringue into parchment-lined 9×12″ baking pan and bake for 45 minutes. Cool on wire rack.

Meanwhile, clean the mixer bowl and whisk attachment. Add whipping cream to bowl and beat on high until medium peaks form. Add the remaining 6 tbsp of sugar and vanilla extract and beat to combine.

To make the lemon mousse:

Place half of the lemon pie fill in a bowl. Add half of the whipped cream and gently fold together to combine.

Once meringue base has cooled, spread remaining 2 cups of lemon pie fill on top, followed by the lemon mousse, and finally the whipped cream. Smooth each layer gently to the edges of the pan as you go. Transfer Lemon Cream Bars to the freezer for 1 hour for easy slicing.