Preheat oven to 325°F (160°C). Prepare an 8-inch (20cm) springform pan by lining the sides and bottom with parchment paper.
Zest and juice the lemon to yield 1 teaspoon of zest and 2 tablespoons of juice.
Separate the egg whites and yolks. Set aside.
In a mixing bowl, beat the cream cheese with an electric mixer until smooth, about 2 minutes. Add condensed milk and beat for another minute. Mix in the egg yolks, lemon zest, and lemon juice until well combined (2-3 minutes).
In a separate clean bowl, beat the egg whites until stiff peaks form.
Gently fold half of the egg whites into the cream cheese mixture. Then fold in the remaining egg whites until fully incorporated and no white streaks are visible.
Pour the batter into the prepared pan. Tap the pan gently to release any air bubbles.
Place a baking sheet on the lower oven rack and pour 2 cups of boiling water onto the sheet. Put the springform pan on the middle rack, above the water bath. Bake for 45 minutes.
After baking, turn off the oven and let the cheesecake cool inside for 30-40 minutes.
Remove the springform pan sides and peel off the parchment paper. Let the cake cool completely before refrigerating for at least 2 hours.
Dust with powdered sugar before serving if desired. Store the cheesecake covered in the refrigerator for up to 3 days.