Preheat the oven to 350ºF (180ºC), and lightly grease or line a 9-inch round cake pan with parchment paper and set aside.
In a small saucepan, melt the butter over medium heat. Stir in the brown sugar and cook until the mixture is smooth and bubbling, about 2 to 3 minutes.
Pour the mixture into the prepared cake pan and gently spread it until it covers the bottom.
Arrange the sliced or chopped strawberries over the brown sugar mixture in an even layer, gently pressing them in so they adhere slightly to the topping.
In a medium bowl, whisk together the flour, baking powder, and salt, and set aside.
In a large bowl, beat or whisk together the brown sugar and vegetable oil until smooth.
Add the egg and vanilla extract and beat until well combined and slightly lighter in color, about 1-2 minutes.
Stir in the flour mixture in three parts, alternating with the milk. Begin and end with the flour, stirring just until combined after each addition. Do not overmix.
Gently spoon the batter over the strawberries, spreading it evenly to the edges of the pan.
Bake for 30 to 35 minutes or until the top is golden and a toothpick inserted in the center comes out clean.
Allow the cake to cool in the pan for 10-15 minutes, then run a knife around the edges and invert carefully onto a serving plate. Make sure to invert the pan while the cake is still warm, otherwise the brown sugar may stick to the pan.
Slice and serve warm (or cooled) with a generous scoop of vanilla ice cream or a generous dollop of whipped cream.