First, make the strawberry reduction by simmering strawberries, sugar, and lemon juice for 20-30 minutes until thick.
Blend for smoothness and refrigerate.
For the cake, preheat the oven to 350F, grease and line three 8-inch pans.
Whisk dry ingredients.
Beat butter, sugar, lemon zest, and vanilla until fluffy.
Add eggs, then alternate adding dry ingredients and milk, ending with flour.
Add lemon juice and divide batter between pans.
Bake for 30-35 minutes and cool.
For the buttercream, beat butter until fluffy, add powdered sugar, strawberry reduction, lemon juice, and heavy cream, and mix until smooth.
Assemble the cake by layering frosting and strawberry reduction between cake layers.
Cover with remaining frosting, pipe decorations, and refrigerate for 2 hours before serving.