01 - Preheat oven to 325°F. Line bottom of 8-inch round cake pan with parchment paper; leave sides ungreased to help cake rise properly.
02 - Whisk flour, sugar, baking powder, and salt in medium bowl until evenly combined.
03 - Whisk egg yolks, Greek yogurt, vegetable oil, vanilla extract, and lemon zest in large bowl until smooth and uniform.
04 - Add dry ingredients to wet mixture and stir just until combined; avoid overmixing to maintain tender texture.
05 - Beat egg whites in clean bowl with electric mixer until stiff peaks form, ensuring maximum volume for airy texture.
06 - Gently fold one-third of beaten egg whites into batter to lighten. Fold in remaining whites carefully, retaining as much air as possible.
07 - Pour batter into prepared pan and smooth top. Bake for 35 to 40 minutes until golden and toothpick inserted in center comes out clean.
08 - Let cake cool in pan for 10 minutes. Run knife around edges, invert onto wire rack, and cool completely before serving.
09 - Dust with powdered sugar before serving if desired. Serve with fresh berries or whipped cream.