Preheat oven to 180 degrees C. Line a 18-20 cm (7-8 inch) cake pan with a circle of parchment paper. Grease well the pan.
Combine flour, salt and baking powder and set aside.
Beat sugar and eggs in a large bowl until the mixture thickens and becomes pale (5-6 minutes).
Add yogurt, vanilla and lemon extract and beat until smooth. Add butter and beat shortly, until combined.
Gradually add the flour and mix gently with a rubber spatula or a wooden spoon until just combined. Pour the batter into the prepared pan.
Bake for 45-55 minutes. Make sure that a wooden skewer inserted in the centre comes out clean or just with a few crumbs. Let the cake cool until room temperature before frosting it.