Strawberry cake 

1. Preheat the oven to 325°F (165°C) and line two 7–8 inch (17–20 cm) round cake pans with parchment paper on the bottoms only.
2. In a large bowl, sift together the cake flour, baking powder, baking soda, and salt.
3. Beat the softened butter and sugar in a large bowl or in a stand mixer fitted with the whisk attachment for about 3 minutes, until pale and creamy.
4. With the mixer running on high speed, add the vanilla extract and egg whites in batches, mixing well for about 1 minute between each addition until smooth. Continue beating for 3–5 minutes more.
5. Using a spatula, fold in the dry ingredients and buttermilk alternately, mixing gently until the batter is smooth and even.
6. Stir in the strawberry purée and a touch of pink food coloring (optional) until fully combined.
7. Divide the batter between the prepared pans, smooth the tops, and tap lightly to release air bubbles.
8. Bake for 25–30 minutes, or until golden and a toothpick inserted in the center comes out clean.
9. Cool in the pans for a few minutes, then transfer to a wire rack to cool completely.
10. Wrap each layer in plastic wrap and chill for at least 2 hours before assembling. Trim the tops if needed for even layers.

Strawberry buttercream :

Follow my recipe for Strawberry Buttercream.

Assembly 

1. Place the first cake layer on a cake board or serving plate.
2. Spread a layer of strawberry buttercream and smooth it with an angled spatula.
3. Add the second layer and cover the entire cake with the remaining buttercream.
4. Decorate with fresh strawberries on top.
5. Serve right away or refrigerate until ready to serve.
6. Bring the cake to room temperature about 20 minutes before serving so the buttercream softens slightly.