Preheat your oven to 350°F (175°C) and line a cupcake tray with liners.

In a medium bowl, whisk together the cake flour, baking powder, baking soda, and salt. Set aside after blending for about 30 seconds.

In another bowl, mix the sour cream, strawberry puree, strawberry extract, and oil until combined. Set aside.

In the bowl of a stand mixer, beat the softened butter until smooth. Gradually add the sugar, mixing on medium speed for 3 to 5 minutes, or until the mixture is fluffy and lightened in color. Add pink coloring gel at this stage if desired.

Incorporate the eggs one at a time, mixing well after each addition until each yolk is fully blended.

On low speed, alternate adding the dry flour mixture and the wet sour cream mixture to the batter, starting and ending with the dry ingredients. (This means adding the dry mix in three parts and the wet mix in two.)

Mix until just combined, then divide the batter evenly among the cupcake liners, filling each with about ¼ cup of batter.

Bake in the preheated oven for 16-18 minutes, or until a toothpick inserted into the center comes out clean or with a few moist crumbs. Let cool.

Cream the softened butter until it’s smooth and creamy. Blend in the vanilla extract.

Gradually add half of the powdered sugar along with most of the milk, beating on medium speed until well combined.

Add the remaining powdered sugar and milk, mixing on medium speed for an additional 3 to 4 minutes. Scrape the sides of the bowl occasionally.

Slow the mixer to the lowest speed for 1 to 2 minutes to help remove any air bubbles. The buttercream should become silky and smooth in texture, perfect for frosting your cupcakes.