Preheat the oven to 375°F (190°C).

Grease a 10" cake pan and set aside.

In a mixing bowl, whisk together the melted butter, sugar, milk, vanilla extract, kosher salt, and orange zest.

Add the chestnut flour and whole blanched almonds to the mixture.

Stir until smooth.

Pour the batter into the prepared cake pan and sprinkle with sliced almonds on top.

Bake until the tart is browned and set, about 25 minutes.

Let the tart cool in the pan for a few minutes before transferring to a wire rack to cool completely.