Preheat oven to 350°. Spray 2 (8-inch) round cake pans with cooking spray. Line bottom of pans with parchment paper.
In a large bowl, stir together brown sugar, cane syrup, and melted butter. Add eggs, vanilla, and orange zest, stirring until well combined.
In a medium bowl, whisk together flour, baking powder, cinnamon, ginger, cloves, and salt. Gradually add flour mixture to sugar mixture alternately with buttermilk, beginning and ending with flour mixture, stirring just until combined after each addition. Carefully whisk in ½ cup boiling water. Divide batter between prepared pans.
Bake until a wooden pick inserted in center comes out clean, 30 to 35 minutes. Let cool in pans for 15 minutes. Remove from pans, and let cool completely on wire racks. Spread Orange Buttercream between layers and on top and sides of cake. Refrigerate until ready to serve. Garnish with sage, rosemary, and orange, if desired.
Orange Buttercream
In a large bowl, beat butter, orange zest, and salt with a mixer at low speed until smooth. Add confectioners’ sugar, 1 cup at a time, alternately with orange juice and milk, 1 tablespoon at a time, beating until smooth. Increase mixer speed to medium, and beat until smooth and fluffy, 2 to 3 minutes. Use immediately.
Recipe by Louisiana Cookin' at https://louisianacookin.com/gateau-de-sirop-2/