Start the strawberry reduction by adding the sliced strawberries into a food processor and pulse until you have about 1 ½ cups puree.
Add the puree into a medium saucepan and heat over medium-high heat, stirring often, until thickened and reduced by about half. This should take about 20 minutes.
Set the reduction aside to cool.
Preheat your oven to 350°F (180°C), or 160°C if using a fan oven, and prepare three 8-inch (20 cm) cake pans by spraying generously with non-stick spray and placing a round of parchment paper in the bottom of each pan.
In a medium bowl, add the sour cream, milk, eggs, vanilla, and cooled puree. Whisk to combine and set aside.
In the bowl of a stand mixer equipped with a whisk attachment, add the flour, sugar, baking powder, and baking soda. Whisk to combine.
Slowly add the room temperature butter into the dry ingredients, 1 tablespoon at a time. Once all the butter is combined, the flour should have a sand-like texture.
With the mixer on low speed, slowly pour half of the wet ingredients into the flour mixture. Mix until combined.
Add the remaining wet ingredients and mix until just combined. Scrape the sides and bottom of the bowl and mix additionally if needed.
Divide the batter evenly between the three prepared cake pans and gently tap on the pans on the counter to release any air bubbles.
Bake for 25 to 27 minutes or until a toothpick inserted in the center of each cake comes out clean.
Remove the cakes from the oven and allow to cool for five minutes, then flip the cakes onto a wire rack to cool completely.
Prepare the frosting by adding the cream cheese and butter into the bowl of a stand mixer equipped with a paddle attachment. Cream on medium-high speed until soft and fluffy, about 3 to 4 minutes.
Scrape the sides and bottom of the bowl and add half of the powdered sugar. Mix until just combined and smooth.
Add the remaining powdered sugar and vanilla extract. Mix until combined and smooth.
Remove the domes off the top of the cake layers if necessary, using a large, serrated knife.
Place one layer of cake on a serving tray and top with about 1 cup of frosting. Smooth evenly. Repeat with the remaining cake layers.
Once the cakes are stacked, smooth a thin layer of frosting over the entire cake.
Place the cake in the refrigerator for 15 to 20 minutes until the frosting crumb coat slightly sets.
Smooth the remaining frosting over the entire cake and smooth. If desired, pipe some frosting around the top border of the cake, and garnish with fresh berries.
Keep refrigerated until ready to serve. Keep leftovers in an airtight container in the refrigerator for up to three days.
