Preheat oven to 350 degrees. Grease and flour a rectangle cake pan and set aside.
Combine sugar, butter, milk, eggs, and vanilla extract in a mixing bowl and stir until uniform.
1 ½ cup granulated sugar, ¾ cup unsalted butter, ¾ cup milk, 4 eggs, 1 teaspoon vanilla extract
In another bowl, whisk together flour, baking powder, and sea salt. Add this dry mixture to the wet mixture and stir until just combined. Do not over mix.
3 cups all-purpose flour, 1 teaspoon baking powder, ¾ teaspoon fine sea salt
Mash or puree strawberries to your desired consistency then stir into cake batter. If adding freeze-dried strawberries, crush or pulse in a blender to form a powder then mix into batter, as well. Batter will be thick.
6 strawberries, ½ ounce freeze-dried strawberries
Spread cake batter into prepared pan. Place on middle oven rack and bake for 30 minutes or until a toothpick inserted into the center of the cake comes out clean. Meanwhile, prepare the frosting.