• Preheat your oven to 350°F and line two 8-inch cake pans with parchment paper, spraying the sides with oil.
  

Make the reduction

• Slice the strawberries and process in a blender until they are smooth.
  
• Transfer to a large pot and bring to a boil on high heat. Once boiling, reduce to medium and simmer, stirring very frequently, until it is reduced by half. You should have just under 1 1/4 cups of purée after reducing. This takes 15 to 25 minutes, depending on how big your pot is.
  

Make the cake:

• In a large bowl, whisk the flour, sugar, baking powder, soda, and salt. Push the mixture to the side of the bowl and spoon in just under 1 cup of the strawberry purée, but don't mix it.
  
• Make three wells in the flour. In one, pour the vanilla, in one the vinegar, and in one the oil. Don't mix.
  
• Pour the water all over the ingredients and then mix together well with a fork.
  
• Divide between the pans and bake until a toothpick inserted in the center comes out clean, about 33 to 36 mins. Allow to cool completely.
  

Frosting:

• Beat the butter in a large bowl until fluffy. Slowly add the powdered sugar a little at a time until well mixed.
  
• Add the remaining strawberry reduction and beat until well mixed.
  

Assemble:

• Place one of the cake layers on a cake stand, bottom side up and spread 3/4 cup of the frosting on top.
  
• Place the other cake on top. Spread a very thin layer of frosting over the cake to seal in the crumbs, then chill for 30 minutes.
  
• Once chilled, frost the rest of the cake and garnish with strawberries, if desired. Then slice and serve.