Preheat the oven: Preheat your oven to 350°F (175°C). Grease and flour two 9-inch round cake pans or line them with parchment paper for easy removal.

1. Prepare the dry ingredients: In a medium bowl, whisk together the flour, baking powder, baking soda, and salt. Set aside.
2. Cream the butter and sugar: Beat the softened butter and sugar together in a large bowl using a hand mixer or stand mixer on medium speed until light and fluffy (about 2-3 minutes).
3. Add eggs and vanilla: Add the eggs, one at a time, beating well after each addition. Stir in the vanilla extract.
4. Alternate dry ingredients and wet ingredients: Gradually add the dry ingredients to the wet ingredients in three parts, alternating with the sour cream and milk. Start and finish with the dry ingredients. Mix just until combined.
5. Add strawberry puree: Stir in the strawberry puree until evenly incorporated.
6. Bake the cake: Divide the batter evenly between the prepared cake pans and smooth the tops. Bake for 25-30 minutes, or until a toothpick inserted into the center comes out clean.
7. Cool the cakes: Let the cakes cool in the pans for 10 minutes, then remove them from the pans and transfer them to a wire rack to cool completely.
8. Prepare the frosting: Beat the softened butter in a large bowl until smooth. Gradually add the powdered sugar, one cup at a time, mixing well after each addition. Stir in the strawberry puree, vanilla extract, and a pinch of salt. If the frosting is too thick, add 1-2 tablespoons of heavy cream or milk to reach your desired consistency.
9. Frost the cake: Once the cakes have cooled, spread a layer of frosting on top of one cake layer. Place the second layer on top and frost the entire cake with the remaining frosting.