Preheat your oven to 350°F (175°C) and lightly grease the baking dish.

In a mixing bowl, whisk together melted butter and brown sugar until smooth and creamy, about 2-3 minutes.

Add the room temperature eggs one at a time, mixing well between each addition until smooth.

Fold in the chopped apples and optional add-ins.

Sift in flour, cinnamon, and a pinch of salt. Stir gently until just combined.

Pour the batter into the prepared baking dish and spread evenly.

Bake for approximately 35 minutes until the edges are light golden brown.

Remove from the oven and cool in the pan for 10-15 minutes before cutting into squares.