Preheat the oven to 350°F (170° C) 150° fan.
Grease and line an 8-inch (20cm) round cake pan with parchment (baking paper)
In a large bowl, beat eggs, sugar and salt and lemon zest (if using) until light and fluffy, about 3 minutes.
Mix in the yogurt, oil, and vanilla extract until well combined.
Then sift in flour and baking powder, and use a wooden spoon or spatula to gently fold them into the mixture until fully incorporated.
Pour the batter into the lined cake pan.
Bake in a preheated oven of 350°F (170° C) 150° fan for between 30-35 minutes.
Remove from the oven, but leave in the pan for 10 minutes. Then turn the cake out onto a cooling rack to cool.
If you plan to frost the cake with buttercream or glaze, allow it to cool completely before decorating. (See note 2)
However, if you're dusting it with powdered sugar, you can do so while the cake is still warm. Complete cooling is not necessary.