Preheat the oven to 350°F. Grease and line three 8-inch cake pans with parchment paper.
In a medium bowl, whisk together 2 ½ cups all-purpose flour, 2 ½ tsp baking powder, and ½ tsp salt. Set aside.
2 ½ cups all-purpose flour, 2 ½ tsp baking powder, ½ tsp salt
In a large mixing bowl, beat the 1 cup unsalted butter and 2 cups granulated sugar until light and fluffy (about 2-3 minutes).
1 cup unsalted butter, 2 cups granulated sugar
Add 4 large eggs one at a time, beating well after each addition. Stir in 1 tbsp vanilla extract.
4 large eggs, 1 tbsp vanilla extract
Alternately add the dry ingredients and 1 cup whole milk and ¼ cup sour cream, beginning and ending with dry ingredients. Mix until just combined.
1 cup whole milk, ¼ cup sour cream
Divide the batter evenly between the cake pans and bake for 28-30 minutes, or until a toothpick inserted in the center comes out clean.
Let the cakes cool in the pans for 10 minutes, then transfer to a wire rack to cool completely.
In a food processor, grind the ½ cup freeze-dried strawberries into a fine powder.
½ cup freeze-dried strawberries
In a large bowl, beat the 1 ½ cups unsalted butter until smooth. Gradually add 4 cups powdered sugar, beating until light and fluffy.
1 ½ cups unsalted butter, 4 cups powdered sugar
Mix in the strawberry powder, 1 tsp vanilla extract, and a pinch of salt. Add 2 tbsp heavy cream, 1 tablespoon at a time, until the frosting reaches a spreadable consistency.
1 tsp vanilla extract, 2 tbsp heavy cream
Place the first cake layer on a serving plate. Spread half of the ¾ cup strawberry jam evenly over the top.
¾ cup strawberry jam
Add the second cake layer, spread the remaining jam, then place the third cake layer on top.
Frost the entire cake with the freeze-dried strawberry buttercream, smoothing it with an offset spatula.
Garnish with fresh strawberries and food-safe flowers (such as roses).