Preheat your oven to 350°F (175°C). Grease and flour a 9x13 inch baking pan.
In a large mixing bowl, combine the yellow cake mix, eggs, sour cream, and vegetable oil. Mix well until the batter is smooth and well combined.
In a separate bowl, mix the chopped strawberries with the sugar and cinnamon. Fold this strawberry mixture into the cake batter.
Pour half of the cake batter into the prepared baking pan and spread evenly. Sprinkle the remaining half of the strawberry mixture over the first layer of batter. Then, pour the rest of the batter on top, smoothing the surface with a spatula.
Bake in the preheated oven for 35-40 minutes, or until a toothpick inserted into the center comes out clean.
Once baked, remove the cake from the oven and allow it to cool in the pan for about 15 minutes before transferring it to a cooling rack.
While the cake is cooling, prepare the strawberry cream icing by beating the softened butter in a mixing bowl until creamy.
Gradually add in the powdered sugar, pureed strawberries, and vanilla extract, mixing until smooth. If the icing is too thick, add milk, one tablespoon at a time, until the desired consistency is reached.
Once the cake is completely cool, spread the strawberry cream icing evenly over the top.
Slice the cake into squares and serve.