Preheat oven to 375°F. Remove butter from the fridge and bring to room temp.
Slice strawberry tops to remove stems. Cut lengthwise into 1/4 inch thick slices. In a 9-10 inch cast iron skillet, mix strawberries and 1/3 cup sugar. Set aside for 10-15 minutes to macerate.
In a small bowl, mix flour, baking powder, and salt. Set aside.
In a medium bowl, cream butter and 1/2 cup sugar until fully mixed, light and fluffy. Beat in egg and vanilla extract. Gradually add flour mixture, stirring until combined. Batter will be sticky, creamy, and pretty thick. If doughy, you need to mix more.
Layer batter into small clumps/spoonfuls over strawberries, covering as much of the strawberry filling as possible. It's OK if there are "holes." A rubber spatula works best for this step.
Bake for 35-40 minutes, until topping is golden brown. Let cool for 5-10 minutes and serve warm with vanilla ice cream or whipped cream.