Preheat your oven to 180°C (160°C fan).
Grease your cake tin with butter.
Line the bottom with baking paper.
This stops the cake from sticking.
Put flour, cocoa, and baking powder together.
Sift them into a large bowl.
Add the caster sugar.
Mix everything well with a spoon.
Crack eggs into another bowl.
Add yoghurt, oil, and vanilla extract.
Whisk them together until smooth.
Make sure everything is well combined.
Pour wet ingredients into dry ingredients.
Mix gently with a spatula.
Don't overmix the batter.
Stop when you see no flour lumps.
Pour batter into your prepared tin.
Smooth the top with a spatula.
Bake for 40-45 minutes.
Check with a skewer inserted in center.
It should come out clean when done.
Let cake cool in tin for 10 minutes.
Then turn it onto a cooling rack.
Let it cool completely before cutting.