Mix together the self-raising flour and baking powder. Sift and set aside.
Preheat oven to 175°C / 350°F.
With the whisk attachment on, beat the butter for 1 minute until softened. Add the sugar and beat until very fluffy and creamy. It takes about 5-6 minutes over medium speed on a stand mixer. Or 8-10 minutes on a hand mixer.
Add the eggs one at a time, waiting for a minute or two until each one is fully incorporated before adding the next one. Then keep beating over high speed until the eggs thicken.
Turn the speed to medium again and add the Greek yogurt. Once fully combined, add the orange zest, Vanilla (or Vanilleta), and orange juice. Beat until combined and then switch off the mixer.
Using a silicone spatula fold the flour and baking powder into the batter. In small batches about 2-3 tablespoons at a time. Don't overmix or apply much pressure as we want to keep that delicate air bubble in the batter.
Butter and line an 8-inch (20 cm) Springform tin. Pour the cake batter and gently smoothen its surface with a spoon. Bake for about 30-35 minutes on the lowest rack of your oven. Test the cake in the center with a toothpick to see if it comes out clean.
Place the cake tin on a large plate and ladle the cooled syrup over the cake. Don't let the cake cool as it won't absorb the syrup properly. The cake needs to be hot.
Let the cake reach room temperature inside the tin. Then remove the ring and carefully overlap the cake over a serving plate. This helps the syrup that has sunk to the bottom of the cake to distribute more evenly.
Cut into 8-10 pieces and serve with a spoonful of Greek yogurt if you like.