Preheat your oven to 350°F (175°C) and prepare a sheet pan.
In a large bowl, cream together the softened butter and granulated sugar until light and fluffy.
Add the eggs, one at a time, mixing well after each addition.
Mix in the vanilla extract and chopped strawberries until evenly combined.
In a separate bowl, whisk together the flour, baking powder, and salt.
Gradually add the dry ingredients to the wet mixture, alternating with buttermilk, starting and ending with the flour.
Pour the batter into the prepared sheet pan and spread it evenly.
Bake in the preheated oven for 25-30 minutes or until a toothpick comes out clean.
Allow the cake to cool in the pan for 10 minutes, then transfer it to a wire rack to cool completely.
While the cake cools, prepare the lemon frosting by creaming together the softened butter and powdered sugar.
Add the lemon juice and lemon zest, mixing until smooth and creamy.
Once the cake is completely cool, spread the lemon frosting evenly on top.
Slice into squares, serve, and enjoy your strawberry sheet cake with lemon frosting!