Preheat the oven to 375 degrees F (190 degrees C). Grease an 8-inch square cake pan.

Stir sugar, milk, vegetable oil, and egg together until well blended. Add flour, baking powder, and salt; stir until incorporated. Pour into the prepared cake pan and sprinkle chopped cranberries over the top.

Combine flour, sugar, and butter for the topping in a bowl and mix until crumbly. Sprinkle over cranberries in the cake pan.

Bake in the preheated oven until a toothpick inserted into the center comes out clean, about 25 minutes. Remove from the oven and allow to cool slightly. Serve warm.