Cook the blueberries with a little sugar over heat until they turn into a blueberry jam.

Beat the eggs, sugar, and salt with a mixer for about 5 minutes until the mixture becomes light, pale, and slightly thick.

Add the oil and mix gently for a short time.

Sift the flour and baking powder together three times.

Add the egg mixture to the flour and baking powder and mix gently until combined.

Add the blueberry jam and mix gently.

Preheat the oven with both top and bottom heat on for 15 minutes at 180°C (356°F).

Pour the batter into a greased cake pan or one lined with parchment paper.

Turn off the top heating element and bake the cake for 30–40 minutes.

In the last 5 minutes, turn the top heat back on.

After about 30 minutes, test the cake by inserting a toothpick—if it comes out clean, the cake is fully baked.

For decoration, mix equal parts cream and cream cheese with a little sugar or powdered sugar. Add some blueberry jam, then top with walnuts.