Begin by carefully separating the egg whites from the yolks, ensuring no yolk contaminates the whites. Set the yolks aside in a mixing bowl and place the egg whites in a clean, dry bowl suitable for whipping.

Using an electric mixer, beat the egg whites on high speed until stiff peaks form, which typically takes about 3-5 minutes. Transfer the whipped egg whites to another bowl, taking care not to deflate them.

In the same mixer bowl, beat the egg yolks alongside monk fruit sweetener and optional vanilla extract until the mixture appears pale and fluffy, about 4-5 minutes.

Mix in the non-fat Greek yogurt to your creamed egg yolk mixture, stirring until smooth and fully blended.

Sift the cornstarch into the yogurt mixture to avoid clumps, then gently fold it in using a spatula until well combined.

Gently fold the stiffened egg whites into the yogurt batter using a spatula.

Line a 7x11 inch baking dish with parchment paper and pour the batter into the prepared dish.

Place the baking dish in a larger baking tray filled with boiling water to create a water bath.

Preheat your oven to 330°F (160°C) and bake the cake for 45 minutes. Then increase the temperature to 350°F (180°C) and bake for an additional 15 minutes.

Once baked, turn off the oven and crack the door open. Allow the yogurt cake to cool in the oven for 1-2 hours.