Prep the pan: Preheat your oven to 320°F (160°C). Grease a 9‑inch (23 cm) round springform pan with butter, line the bottom with parchment paper, and lightly dust the sides with flour.

Create the cheese-yoghurt mixture: In a heatproof bowl over a simmering water bath (double boiler), melt together the butter, cream cheese, and heavy cream until smooth. Remove from heat and whisk in the yoghurt and salt until fully incorporated. Let cool slightly.

Incorporate dry ingredients: Sift the flour and cornstarch into the cheese‑yoghurt mixture. Stir gently just until combined — do not overmix.

Beat egg yolks & lemon juice: In a small bowl, whisk the egg yolks lightly with lemon juice until well combined. Gently fold into the cheese‑yoghurt batter.

Whip egg whites: In a clean mixing bowl, beat the egg whites with cream of tartar until foamy. Gradually add the sugar in two or three batches, continuing to whisk until stiff, glossy peaks form.

Fold carefully: Gently fold one-third of the meringue into the batter to lighten it. Then, fold in the remaining meringue with gentle sweeping motions until no streaks remain—be careful not to deflate the batter.

Transfer & bake: Pour the batter into the prepared pan. Place the pan in a larger roasting pan and add hot water (bath) until it reaches halfway up the sides of the springform pan. Bake for about 60–70 minutes, or until the top is lightly golden and a skewer inserted into center comes out clean or with just a few moist crumbs.

Cool gradually: Turn off the oven, crack open the door slightly, and let the cheesecake cool in the oven for another 30 minutes to prevent cracking.

Chill before serving: Remove from oven, cool completely at room temperature, then refrigerate at least 2–3 hours (or overnight). Dust with confectioners’ sugar just before serving, if desired.