Preheat the oven to 350˚F (175˚C). Spray a 9-inch round cake pan (with at least 2-inch tall sides) with baking spray. Line the bottom of the pan with parchment paper and spray parchment paper lightly. Set aside.

In a medium-large bowl whisk together the sugar, buttermilk, eggs and vanilla until well combined.

Add the baking powder and salt and stir until well incorporated and no lumps of baking powder remain. Add the all-purpose flour and almond flour. Stir just until the flour disappears.

Add the oil and stir well. At first, it will seem to separate, but keep stirring till smooth.

Pour the batter into the prepared pan. Bake for 35-45 minutes, until the cake feels springy to the touch in the center and a toothpick or cake tester inserted into the center comes out clean. You can also use an instant thermometer to determine if the cake is done. The temperature when done should be 205-210˚F (96-98.8C). Check the cake after 30 minutes and tent it with foil if the top is getting brown but the cake is not quite done. Leave the oven on.

Allow the cake to cool for 10 minutes, then turn it out of the pan onto a cooling rack. The bottom will be the top that you add the caramel topping to. Set a timer for 20 minutes. In the meantime, prepare the topping.

Place the pecans in a medium-size baking pan (I use another cake pan) and toast in the oven for 6 minutes. Remove and set aside to cool. The oven can be turned off now.

While the pecans are toasting, make the caramel sauce. Combine the butter, brown sugar and syrup in a medium-size bowl. Microwave on high power for one minute until the butter is melted. Remove from microwave, stir well then return to microwave for another minute.

Add the half and half and vanilla. Stir until smooth then microwave for another 30 seconds. Add the pecans, stir and set aside. The mixture will be quite loose at first, but it will thicken as it cools.

After a total of 30 minutes, cooling time, add the caramel pecan topping to the cake. Leave the cake turned upside down. Start with about three-quarters of it in the center of the cake and spread right to the edges. Use the remainder of the topping to cover any bare spots. (If the caramel topping seems too thick to spread, just pop it back in the microwave for 20 seconds.)

Sprinkle lightly with flaky sea salt, if desired. Allow the cake to cool completely (if you have the will power) then slice and enjoy!I