Preheat the oven to 350°F (180°C). Spray 3 (8-inch) round cake pans with baking spray with flour, and line with parchment paper.

In a large bowl, whisk together sugar, flours, salt, baking powder, baking soda, salt, ginger, cinnamon and nutmeg.

In a separate large bowl, whisk together buttermilk, oil, eggs, bourbon, and vanilla. Add in sugar mixture, and whisk until smooth and combined. While whisking, slowly add 1 cup (240 grams) warm water, whisking until just combined. (Batter will be very thin.). Divide batter evenly between prepared pans (about 2¼ cups or /620 grams).

Bake until set and a wooden pick inserted in center comes out with a few moist crumbs or an instant-read thermometer inserted near in center registers 200°F (93°C) to 205°F (96°C), 35 to 38 minutes. Let cool in the pans on a wire rack for 20 minutes. Run a thin knife around the edges of the pan, and invert onto a parchment- lined baking sheet to finish cooling.

Spread Buttercream between cooled cake layers and on top and sides of cake, as desired. Garnish with toasted salted pecans, if desired.