Preheat oven to 350* F Topping: heat butter, brown sugar, and syrup in saucepan, heat until sugar is dissolved. Stir in pecans. Apply thin layer of Cake Pan Mousse on bottom and sides of 10” round or square baking pan.

Spread Topping evenly on bottom of pan. Set aside.

Swirl: Whisk together cinnamon and brown sugar; set aside.

Cake: Whisk all-purpose flour, baking powder, and baking soda together in a medium bowl.

Whisk room-temperature sour cream, eggs, granulated sugar, neutral oil, water, vanilla extract, and kosher salt in a large bowl until smooth. Working in two batches, stir in the flour mixture until the batter is just smooth (do not overmix).

Dollop half of the batter (about 1 1/2 cups) over the pecans, then spread into an even layer. Sprinkle evenly with the cinnamon-sugar mixture. Dollop with the remaining batter and carefully spread into an even layer, covering the sugar mixture.

Bake until deep golden-brown and a toothpick inserted into the center comes out clean, 35 to 40 minutes. Check after 30 minutes: If the cake is browning too much, tent it lightly with aluminum foil.

Let the cake cool in the pan for 10 to 15 minutes. Run a thin knife along the edge to loosen the cake. Invert the cake onto a large plate and sprinkle with flaky salt if desired. Let cool until room temperature. Serve with vanilla ice cream.

NOTE: (a) The cake can be stored in an airtight container at room temperature for up to 2 days. (b) As you can see in the picture, the corners stuck to the pan, it came out easily, after the cake was turned out. I had the bright idea to use parchment paper, thinking it’d turn out better, it didn’t. I think that’s why the corners came off.