Preheat the oven to 350°F (175°C). In a saucepan, combine melted butter, brown sugar, and vanilla extract over medium heat until the sugar dissolves. Pour this mixture into the bottom of the cake pan.

Arrange the halved apricots, cut side down, in the caramel mixture in the pan.

In a mixing bowl, whisk together flour, baking powder, salt, and granulated sugar.

In another bowl, mix milk, vegetable oil, egg, and vanilla extract until well combined.

Pour the wet ingredients into the dry ingredients and stir until just combined.

Pour the cake batter over the apricots in the pan, smoothing the top with a spatula.

Bake in the preheated oven for 30-40 minutes, or until a toothpick inserted into the center comes out clean.

Let the cake cool in the pan for 10 minutes before inverting onto a serving plate.