Preheat oven to 350°F (175°C). Grease a 9-inch round cake pan.
Prepare topping:
Melt butter and brown sugar in a small pan until bubbly. Pour into the cake pan and spread evenly. Arrange strawberries cut-side down on top.
Mix dry ingredients:
In a bowl, whisk together flour, baking powder, and salt.
Cream butter & sugar:
In another bowl, beat butter and sugar until light and fluffy.
Add eggs & vanilla:
Beat in eggs one at a time, then add vanilla extract.
Combine:
Add dry ingredients in batches, alternating with milk. Mix until smooth.
Assemble:
Pour batter over strawberries and spread evenly.
Bake:
Bake for 35–40 minutes or until a toothpick comes out clean.
Cool & flip:
Let cool for 10–15 minutes, then carefully invert onto a plate.