Mix the butter and sugar in a large bowl until light and fluffy, then beat in the eggs one at a time.
Measure the flour, salt, and baking powder together, then whisk to combine. Mix the vanilla and milk together in a measuring cup.
Beat in the half the flour then all the milk, then the rest of the flour, just until the flour is mixed in.
Pour the batter over the fruit and smooth with a spatula.
Bake in a 350-degree oven for 40-45 minutes, or until golden brown and bubbly.
Remove cake from oven and let sit for 10 minutes.
With oven mitts, place a serving plate over the skillet and gently flip the cake upside down onto the plate.