Center a rack in the oven and preheat the oven to 350 degrees F. Butter a seasoned 9-inch cast-iron skillet or other heavy ovenproof skillet, a 9-inch cake pan or even a pie pan.

Pour the sugar into a medium bowl. Add the zest and blend the zest and sugar together with your fingertips until the sugar is moist and aromatic. Whisk in the eggs one at a time until well blended. Whisk in the salt and the extracts. Switch to a rubber spatula and stir in the flour. Finally, fold in the melted butter.

Scrape the batter into the pan and smooth the top with a rubber spatula. Scatter the sliced almonds over the top and sprinkle with a little sugar. If you’re using a cake or pie pan, place the pan on a baking sheet.

Bake the cake for 25 to 30 minutes, or until it is golden and a little crisp on the outside; the inside will remain moist. Remove the pan from the oven and let the cake cool for 5 minutes, then run a thin knife around the sides and bottom of the cake to loosen it. You can serve the cake warm or cooled, directly from the skillet or turned out onto a serving plate.