In a bowl, whisk together the melted butter and sugar. Add the eggs and vanilla extract and whisk until smooth.
Fold in the cocoa powder, flour, salt, and baking powder until just combined. Do not overmix - a few streaks of flour are fine.
Spoon the batter into a greased silicone muffin mold filling each cup about halfway. Press one soft caramel candy into the center of each, then top with more batter to cover the caramel completely.
Preheat the air fryer to 325F. Place the mold in the basket and air fry for 12-14 minutes until the tops are set and a toothpick inserted near the edge comes out with moist crumbs. The center will be gooey from the caramel.
Let cool in the mold for 5 minutes, then carefully remove. Sprinkle each brownie bite with a pinch of flaky sea salt and serve warm while the caramel center is still melty.