Grease a 9” cast iron skillet (or round cake pan) with butter. Preheat the oven to 350°F.
In a medium bowl, whisk together the eggs, sugar, and orange zest until well blended. Add the salt, vanilla, and almond extract; whisk until well combined.
Add the flour to the bowl, and gently stir until well combined. Fold in the melted butter until a smooth batter forms.
Pour the batter into greased skillet and smooth top with the spatula. Sprinkle the sliced almonds and course sugar evenly across the top of the batter.
Bake at 350°F until top is golden and edges are slightly crisp. Allow cake to cool for 5 minutes before slicing or transferring to a serving plate. Garnish with a light dusting of powdered sugar (optional); serve warm or at room temperature.