Preheat your oven to 350°F (175°C) and grease a 9x13 inch baking pan.

In a large mixing bowl, cream together the softened butter and granulated sugar until fluffy.

Add the eggs one at a time, mixing well after each addition.

Stir in the milk and vanilla extract until well combined.

In another bowl, whisk together the flour, baking powder, and cinnamon. Gradually add this dry mixture to the wet ingredients, mixing until just combined.

Fold in the diced strawberries.

Pour half of the batter into the prepared pan, then sprinkle a mixture of cinnamon and sugar on top. Pour the remaining batter over it.

Using a knife, swirl through the batter to create a marble effect.

Bake for 30-35 minutes or until a toothpick inserted in the center comes out clean.

For the icing, mix the powdered sugar, strawberry jam, and enough milk to reach your desired consistency. Drizzle over the cooled cake before serving.