Preheat your oven to 160°C (340°F) and line the bottom of a 20 cm springform pan with parchment paper.
Separate the egg whites and egg yolks into two separate mixing bowls.
In the bowl with the yolks, combine the condensed milk, Greek yogurt, lemon juice, and lemon zest. Mix until smooth and fully blended, then set aside.
In the bowl with the egg whites, use an electric mixer or stand mixer to beat them until stiff peaks form.
Carefully fold the beaten egg whites into the yolk mixture in batches, using a spatula and gentle folding motions to keep the mixture airy.
Pour the final batter into the prepared springform pan. Place this pan inside a larger baking tray or dish, then fill the outer tray with water until it reaches about 3 cm up the sides of the springform pan.
Bake for 45 minutes, then turn off the oven and leave the cake inside to cool completely before removing.
Once cooled, refrigerate the cake for 2 to 3 hours, or preferably overnight, to set.
Before serving, dust the top with powdered sugar if desired, slice, and enjoy.
