Heat the oven to 350ºF. Coat a 9-inch round cake pan with butter or cooking spray. Place on an aluminum-foil lined baking sheet.

Place ½ cup packed brown sugar, 1 stick unsalted butter, ¼ cup honey, and ⅛ teaspoon kosher salt in a small saucepan. Cook over medium-low heat, stirring frequently, until the butter is melted and the sugar is just dissolved.

Stir in 1 ¼ cups coarsely chopped raw pecans. Transfer to the cake pan and spread into an even layer.

Whisk 1 ½ cups all-purpose flour, 1 ½ teaspoons baking powder, and ½ teaspoon baking soda together in a medium bowl.

Whisk ¾ cup room-temperature sour cream, 2 room-temperature large eggs, ¾ cup granulated sugar, ½ cup neutral oil, ¼ cup water, 1 teaspoon vanilla extract, and ½ teaspoon kosher salt in a large bowl until smooth. Working in two batches, stir in the flour mixture until the batter is just smooth.

Stir ¼ cup packed brown sugar and 2 teaspoons ground cinnamon together in the now-empty flour mixture bowl.

Dollop half of the batter (about 1 ½ 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 if desired.