• Preheat your oven to 350°F (175°C). Grease and flour a 9x13-inch sheet cake pan, lining the bottom with parchment paper for easy removal.
• In a medium bowl, combine the cake flour, baking powder, baking soda, and salt. Whisk until well blended, then set aside.
• In a separate bowl or large measuring cup, mix together the sour cream, strawberry puree, vanilla extract, and strawberry extract (if you are not using Jello powder). Blend with a fork until smooth, and set aside.
• Using a stand mixer or hand mixer, beat the softened butter on medium speed until smooth. Gradually add the sugar (and strawberry Jello powder if not using strawberry extract), mixing on medium speed for about 3 to 5 minutes, until light and fluffy.
• Add the eggs one at a time, ensuring each egg is fully incorporated before adding the next. If you’re adding red or pink coloring, do so at this stage or anytime during the mixing process.
• Reduce mixer speed to low. Begin adding the flour mixture and sour cream mixture alternately, starting and ending with the flour mixture (three additions of dry ingredients and two of wet). Mix until just combined; avoid overmixing.
• The batter will be thick. Spread it evenly into your prepared cake pan, smoothing the top with the back of a spoon or offset spatula. Tap the pan lightly on the counter to release any trapped air bubbles.
• Bake in the preheated oven for 30-35 minutes, or until a toothpick inserted into the center of the cake comes out clean or with just a few crumbs attached. Oven times can vary, so start checking around 30 minutes. Allow the cake to cool in the pan for 5-10 minutes before turning it out onto a wire rack to cool completely.

For the Frosting

• Beat the softened butter on low to medium speed until creamy and smooth. Add the cream cheese, continuing to mix on low to medium speed until well incorporated and smooth.
• Blend in the vanilla extract, followed by gradually adding the powdered sugar. Beat on low speed until fully blended and smooth, then mix in the strawberry puree. If tinting the frosting, add coloring gel at this stage.
• Continue mixing until the frosting is creamy and well combined. Store the frosting in the refrigerator if making in advance, allowing it to sit at room temperature before use and remixing if needed.
• Frost the cooled cake as desired. We used an offset spatula to create a decorative pattern and garnished with fresh strawberries on top.

Storing the Cake

• Because of the cream cheese frosting, refrigerate the cake in an airtight container, a sealed bakery box, or under a cake dome. For the best texture and flavor, remove from the refrigerator 2-3 hours before serving to allow the cake and frosting to soften and reach room temperature.