Preheat the oven to 170°C.
Line two 6 inch cake pans with baking paper. Cover the base and the wall of the cake pans.
Add flour, baking powder and salt in a mixing bowl. Stir with a whisk to distribute evenly. Set aside.
Pour milk into a heatproof measuring cup and add butter.Microwave for 1 minute. Stir and make sure butter is melted. Set aside.
In another big mixing bowl, beat egg, sugar and vanilla extract on medium speed until light and creamy, about 1 minute and a half. Add your milk-butter mixture gradually on low speed until well mixed.
Add your flour mixture to your wet ingredients and mix on low speed, until just combined. Scrape your mixing bowl and fold with spatula to ensure thorough mixing.
Divide cake batter evenly between the two lined cake pans.
Bake in the middle oven rack for 35 to 38 minutes until a toothpick inserted in the middle of the cake comes out clean.
Remove your cakes from the oven and allow to cool for 10 minutes. Run a butter knife along the sides if necessary, and flip your cake pan to remove your cakes. Allow to cool completely on a wire rack. Cut both layers in half horizontally into 4 evenly layers.