Preheat the oven to 350 degrees F. Coat a 9-inch springform pan with cooking spray. Then line the bottom of the pan with parchment paper and coat the paper with cooking spray.

Melt the chocolate and butter in a large heatproof bowl set over a saucepan filled with 1 inch of barely simmering water and stir until smooth. Make sure the bottom of the bowl does not touch the boiling water. Remove the bowl from the heat and stir in the oil, vanilla, cinnamon, chile powder and salt.

In the bowl of a standing mixer fitted with a whisk attachment, or with a hand-held mixer beat the eggs and sugar on medium-high speed until light in color, about 3 to 4 minutes. Using a spatula or wooden spoon, fold in the chocolate mixture until combined. Pour the batter into the prepared pan. Bake the cake until the top is just set and beginning to crack, and a toothpick or wooden skewer inserted into the center comes out moist but not really wet, about 35 minutes. Let the cake cool completely in the pan on a wire rack for about 1 hour. Remove the sides of the springform pan.

Cover the cake and refrigerate for at least 3 hours or up to 3 days. Let the cake stand at room temperature for about 30 minutes before serving. Dust with confectioners' sugar and serve with whipped cream, if desired.