Preheat oven to 350°F (175°C). Pour melted butter into a baking dish, ensuring it evenly coats the bottom.

In a mixing bowl, whisk together almond flour, baking powder, and salt until well combined.

In a separate bowl, beat eggs, heavy cream, and apple cider vinegar until smooth and fully incorporated.

Pour the wet ingredients into the dry ingredients and mix until a thick batter forms.

Transfer the batter to the butter-filled baking dish, spreading it evenly while allowing the butter to rise around the edges.

Bake for 22-25 minutes, or until golden brown and a toothpick inserted in the center comes out clean.

Let cool slightly, then slice into squares and serve warm.