In a wide add room temperature butter (softened butter ) and sugar.
Beat it on low to medium speed in an electric hand beater until it combines well. To it, add eggs and beat well. Make it a note, add one egg at a time, and beat on low speed.
The consistency has to be creamy, as shown in the picture.
Sift all-purpose flour, salt, and baking powder into the wet ingredients.
Beat the flour mixture on medium speed in an electric hand mixer. You can also mix with a spatula to mix the cake batter. Use the cut-and-fold method while using a spatula. The cake batter will be slightly thick. To loosen the batter, add milk a little at a time until you reach the perfect smooth cake batter, as shown in the picture.
Finally, add vanilla extract and gently fold until it is well combined.
Meanwhile, preheat oven to 180 C (356F). Grease the mould with butter and line it with parchment paper. Transfer the cake batter to two square cake moulds (20.3 *20.3 * 7.6 cm). Gently smoothen the surface with a spatula and tap the tray on the kitchen counter to remove air pockets in the cake batter.
Bake it in the oven for 30 to 35 minutes or until an inserted skewer comes clean. Transfer it to a cooling rack. Remove the parchment paper and let it cool completely.
Slice and serve it with a cuppa of coffee or milk for morning breakfast, snack, or dessert. It is perfect for a kid's snack box.