Blend strawberries until smooth. Strain through a fine-mesh sieve. Simmer puree with sugar and lemon juice over medium heat for 15 to 20 minutes until reduced by half. Cool completely. Reserve 1/2 cup for batter, 1/4 cup for frosting.
Preheat oven to 350 degrees F. Grease pans, line with parchment, grease parchment.
Whisk flour, baking powder, baking soda, and salt together in a bowl. Set aside.
Beat butter on medium-high for 3 minutes until pale. Add sugar and beat 2 more minutes.
Add egg whites one at a time, beating after each. Add vanilla extract.
With mixer on low, add strawberry reduction, sour cream, and optional food coloring.
Add flour mixture in three additions, alternating with milk in two additions. Mix on low until just combined.
Divide between prepared pans. Bake 28 to 32 minutes until toothpick comes out clean.
Cool in pans 10 minutes, turn onto wire rack, cool completely.
For frosting: beat cream cheese and butter until smooth, 2 to 3 minutes. Add powdered sugar cup by cup on low. Add reduction, vanilla, salt. Beat on medium 1 to 2 minutes until thick.
Level layers. Assemble with frosting between layers. Apply crumb coat, refrigerate 20 minutes, apply final layer.