1. Preheat the oven to 350°F (175°C) and allow it to preheat while you prepare your batter.
2. Cream the softened butter and granulated sugar in a large mixing bowl using an electric mixer until light and fluffy, about 3-4 minutes.
3. Add the eggs one at a time, beating well after each addition to keep the batter smooth.
4. In a separate bowl, sift together the all-purpose flour, baking powder, and salt to combine and ensure the flour is lump-free.
5. Gradually add the dry ingredients to the butter mixture, alternating with the milk. Start and end with the dry ingredients. Mix on low speed until just combined, avoiding overmixing.
6. Stir in the vanilla extract and any additional flavorings, like lemon zest or cocoa powder, based on your preference.
7. Pour the batter evenly into 4-inch cake pans lined with parchment paper, smoothing the tops with a spatula.
8. Bake the cakes for 18-22 minutes or until a toothpick inserted into the center comes out clean.
9. Remove the cakes from the oven and let them cool in the pans for 10 minutes before transferring to a cooling rack to cool completely.
10. Level the cakes if they have domed tops using a serrated knife for a flat surface.
11. Slice each cake horizontally to create layers if you wish to add filling, but this step is optional.
12. Brush cake layers lightly with simple syrup if additional moisture is needed.
13. Place the first cake layer on a cake board or plate to begin decorating.
14. Apply a thin crumb coat of frosting to seal in crumbs, then chill the cake for 15-20 minutes to set the coat.
15. Use an offset spatula to evenly apply a second layer of frosting. Smooth it out for a clean finish.
16. Decorate the cake as desired, using tools like piping bags for intricate designs, adding sprinkles, or creating a themed decoration.
17. Store leftover cake appropriately: at room temperature in an airtight container for up to 24 hours or in the fridge for up to 3 days if it contains perishable filling or frosting.
18. For long-term storage, freeze the cake wrapped in plastic wrap and foil, keeping it in a freezer-safe container for up to 2 months.
19. When ready to serve, thaw frozen cake overnight in the fridge, then bring it to room temperature before cutting and enjoying.