Preheat your oven to 350°F (175°C) and prepare a 9-inch round cake pan.

In a large mixing bowl, combine plain Greek yogurt, large eggs, granulated sugar, softened unsalted butter, and vanilla extract. Whisk until smooth.

In a separate bowl, sift together all-purpose flour, baking powder, and salt. Mix in lemon zest if using.

Gradually add the dry mixture to the wet mixture, stirring gently until combined.

Pour the batter into the prepared cake pan and smooth the top with a spatula.

Bake for 25-30 minutes until a toothpick inserted comes out clean and the top is golden.

Cool in the pan for 10 minutes, then transfer to a wire rack to cool completely.

Dust the top with powdered sugar before serving.