Preheat oven to 350°F (175°C). Grease three 9-inch round cake pans and line with parchment paper.
Sift together flour, baking powder, baking soda, and salt into a large bowl; set aside.
In a separate bowl, beat 340g (1 1/2 cups) butter and 2 cups granulated sugar until fluffy (3 minutes).
Add eggs, one at a time, mixing well after each addition. Stir in 1 tbsp non-alcoholic vanilla extract.
Alternate adding the dry ingredients and buttermilk to the butter mixture, begin and end with the dry ingredients. Mix until fully combined.
Divide batter among the prepared pans. Bake for 35–40 minutes or until golden and a toothpick inserted comes out clean. Cool in pans 10 minutes, then invert onto wire racks to cool completely.
For frosting: In a large bowl, beat 340g (1 1/2 cups) softened butter with 1 tbsp non-alcoholic vanilla extract.
Add powdered sugar 1 cup at a time, mixing on low speed to avoid air pockets. Gradually add milk/cream until desired consistency is achieved.
Assemble cake by placing one layer on a cake stand or plate. Spread a third of the frosting evenly on the top and sides, then add the second layer and repeat, finishing with the final layer and remaining frosting. Garnish as desired.