Heat your oven to 180°C.
Line the baking tray with parchment paper.
This stops the cake from sticking.
Grease the paper lightly with butter.
Put flour and baking powder in a bowl.
Add the brown sugar too.
Mix everything together with a spoon.
Make sure there are no lumps.
Crack the eggs into the mixture.
Pour in the sunflower oil slowly.
Mix until everything is smooth and combined.
Don't over-mix the batter.
Fold in the grated carrots gently.
Add the chopped walnuts next.
Stir until everything is evenly spread.
The batter will be thick.
Pour the batter into your prepared tray.
Spread it evenly with a spatula.
Bake for 35-40 minutes in the oven.
Check with a skewer until it's clean.
Beat cream cheese and butter together.
Add icing sugar gradually while mixing.
Add vanilla extract at the end.
Mix until light and fluffy.
Let the cake cool completely on a rack.
Spread the frosting evenly on top.
Cut into squares and serve immediately.