Preheat the oven to 350°F (175°C). Place the butter in a 9x13-inch baking dish (about 23 x 33 cm) and let it melt in the oven as it preheats.
In a bowl, toss the strawberries with 1/3 cup sugar (67 g). Let them sit for 10 to 15 minutes.
In a separate bowl, whisk together the flour, the remaining 2/3 cup sugar (133 g), baking powder, and salt.
Add the milk and vanilla extract. Whisk just until smooth.
Remove the baking dish from the oven. Spread the strawberries and their juices over the melted butter.
Pour the batter evenly over the strawberries. Do not stir.
Bake for 30 to 35 minutes, until the top is golden brown and the fruit is bubbling around the edges.
Cool for 10 to 15 minutes, then serve warm.