Step 1

Preheat the oven to 350 degrees F.

Step 2

Lightly coat a jellyroll pan with cooking spray.

Step 3

Sift the all-purpose flour, the baking powder, and the salt together in a medium bowl and set it aside.

Step 4

Beat the granulated sugar and 1 cup of the butter in a large bowl with an electric mixer on medium speed until it is light and fluffy, about 4-5 minutes.

Step 5

Add the eggs, one at a time, to the butter mixture and beat well after each addition.

Step 6

Beat the vanilla extract into the sugar mixture.

Step 7

Add the flour mixture to the sugar mixture, 1/3 at a time, alternating with the cream soda and ending with the flour mixture, beating after each addition on low speed just until it is smooth.

Step 8

With a spatula, fold 1/2 cup of the pastel sprinkles into the batter.

Step 9

Spread the batter in the prepared pan and gently tap the pan on a countertop surface to release any bubbles.

Step 10

Bake the batter until a wooden pick inserted into the center of cake comes out clean, about 20-25 minutes.

Step 11

Transport the cake to a wire cooling rack and allow it to cool for 1 hour.

Step 12

Process the freeze-dried strawberries in a food processor until they are crushed to a fine powder, about 1 minute.

Step 13

Beat the powdered sugar and the remaining butter in a large bowl with an electric mixer on medium speed until it is well-blended.

Step 14

Add the strawberry powder to the butter mixture and beat on medium-high speed until fluffy, about 4 minutes.

Step 15

Add the sour cream to the strawberry mixture, 1 tablespoon at a time, and beat after each addition until it is just combined.

Step 16

Continue to beat the buttercream on medium-high speed until it is creamy and spreadable, about 3 minutes.

Step 17

Add the whole milk to the buttercream to reach the desired texture, if necessary.

Step 18

Spread the buttercream over the cooled cake with a spreading knife.

Step 19

Garnish the cake with the remaining sprinkles.

Step 20

Slice and serve.