1. Make the strawberry reduction. Blend the strawberries until completely smooth. Pour into a medium saucepan with the sugar, lemon juice, lemon zest, and a pinch of salt.

2. Bring the mixture to a simmer over medium heat, then reduce the heat to medium-low and cook, stirring occasionally, until very thick and reduced to about 1 cup, with a texture similar to tomato sauce (about 40–60 minutes). Transfer to a bowl and let cool to room temperature.

3. Prepare for the cake. Bring the butter, egg whites, milk, and the measured 6 ounces of strawberry reduction to room temperature. Grease and line two 8-inch round cake pans and preheat the oven to 350°F (176°C).

4. Make the wet mixture. In a medium bowl, whisk together the milk, oil, 6 ounces strawberry reduction, strawberry emulsion or extract, vanilla extract, lemon juice, lemon zest, and pink gel food coloring. Set aside.

5. Make the dry mixture. In another bowl, whisk together the flour, baking powder, baking soda, and salt. Set aside.

6. Cream butter and sugar. In a stand mixer fitted with the paddle attachment, beat the room-temperature butter on medium speed until smooth and shiny, about 30 seconds. Gradually add the sugar and beat until very light and fluffy, 3–5 minutes.

7. Add egg whites. With the mixer on medium, add the egg whites one at a time, beating about 15 seconds between each addition, until the mixture looks cohesive and creamy.

8. Combine wet and dry. On low speed, add about one-third of the dry ingredients to the batter, followed immediately by about one-third of the strawberry-milk mixture. Mix just until almost incorporated, then repeat twice more, alternating dry and wet, scraping the bowl as needed. Stop mixing as soon as the batter is smooth and thick.

9. Bake the cakes. Divide the batter evenly between the prepared pans and smooth the tops. Bake at 350°F (176°C) for 30–35 minutes, or until the centers feel set and a toothpick comes out clean or with a few moist crumbs.

10. Cool the layers. Let the cakes cool in their pans on a rack for 10 minutes, then turn them out onto the rack to cool completely. Once cool, wrap each layer in plastic wrap and refrigerate at least 2 hours or freeze up to 1 week before assembling.

11. Make the strawberry buttercream. In a stand mixer bowl, combine the pasteurized egg whites and powdered sugar. With the whisk attachment, mix on low to combine, then whip on high for about 5 minutes until thick and glossy.

12. Add the butter. With the mixer on high, add the softened butter in chunks and whip for 8–10 minutes, until the buttercream is very light, white, and fluffy. It may look curdled at first—keep whipping until it smooths out.

13. Flavor the frosting. Add the strawberry reduction, vanilla extract, and salt, and whip until fully incorporated and smooth. For extra-smooth frosting, switch to the paddle attachment and mix on low for 15–20 minutes to remove air bubbles.

14. Assemble the cake. Level the chilled cake layers if needed. Place the first layer on a cake stand. Spread a thin layer of strawberry reduction on the cake if desired, then add an even layer of strawberry buttercream.

15. Add the second layer. Place the second cake layer on top and gently press to level. Frost the top and sides of the cake with the remaining strawberry buttercream, smoothing or adding swirls as desired.

16. Decorate and serve. Garnish the cake with fresh strawberries if you like. Slice and serve at room temperature for the best texture and flavor.