Preheat the oven to 350°F,lightly grease three 6-inch cake pans with vegetable oil and line the bottom with a round of parchment paper.

Reduce the strawberry purée. In a small saucepan over medium-low heat, cook the strawberry puree, stirring often, until thick and bubbly and reduced to 1/3 cup, about 10-15 minutes. Transfer to a bowl and place in the fridge until completely cool.

In a medium mixing bowl, whisk together flour, baking powder, baking soda, and salt. Set aside.

In the bowl of a stand mixer with paddle attachment or a large mixing bowl with a hand mixer, cream the butter and sugar together until light and fluffy, 2-3 minutes, scraping down the sides. Add the egg and egg whites one at a time and beat until completely mixed, scraping down the sides as needed. Add the sour cream and vanilla and mix until just combined, scraping down the sides as needed.

Add the flour mixture in two parts, alternating with the milk, scraping down the sides as needed, mixing until just combined. Be careful not to over mix.

Add the strawberry puree and mix on low just until completely combined.

Evenly divide the cake batter among the three cake pans, smoothing out the top.

Bake for 28-32 minutes, until the center springs back when poked and a toothpick comes out clean or with just a few dry crumbs. Remove from heat and let cool for 10 minutes. Run a butter knife around the outside before overturning the cakes upright onto a wire rack to cool completely before frosting.

Roughly chop half the strawberries into ¼-inch pieces and set aside. Wash remaining strawberries for topping.

Prepare the frosting. In the bowl of a stand mixer fitted with the paddle attachment or a medium mixing bowl with a hand mixer, beat the cream cheese until smooth over medium speed. Add the butter and cream together over medium speed, scraping the sides as you go.

With the mixer on low, slowly add the powdered sugar, vanilla, and salt. Beat until smooth.

To frost the cake, place one cooled cake layer on your cake stand or platter. Top with about ½ cup frosting and spread evenly to the edges. Top with ½ of the chopped strawberries, leaving a 1-inch border of frosting around the outside. Repeat with another cake layer. Top with final cake layer and spread remaining frosting over the top and on the sides. Use a large offset spatula or bench scraper to smooth and scrape frosting off the sides as pictured. Smooth the top of the cake and top with remaining strawberries, whole or halved.

Chill the cake for 20-30 minutes before slicing. Store leftovers covered in the fridge and bring to room temperature before serving.