Preheat oven to 275°F. Thoroughly grease a 7 inch pie plate with butter or coconut oil.
In a small bowl, use a hand mixer to beat the egg whites and cream of tartar with a hand mixer until soft peaks form. With the mixer on low, slowly sprinkle in the sweetener until completely incorporated.
Beat until stiff peaks form. Gently mix in the collagen, gelatin and extract.
Spoon the mixture into the greased pie plate, then smooth the mixture across the bottom, up the sides, and onto the rim of the pie plate to form a shell. Cook for 1 hour, then turn off the oven and let the crust stand in the oven for another 20 minutes.
Meanwhile, place the heavy cream in a large cool bowl and whip with electric hand mixer on high until soft peaks form. Add the sweetener and beat until medium peaks form; taste to adjust sweetness to your liking. Place cream over the top of the chilled pavlova.
Top with sliced strawberries and serve in slices.
Store in an airtight container in the refrigerator for up to 3 days before filling.