Preheat oven to 350°F. Butter 1 (12-inch-wide, 2-inch-tall) round cake pan; line bottom with parchment paper.

Sift together flour and baking powder into a large bowl. Set aside.

Beat egg whites and salt in a stand mixer fitted with a whisk attachment at medium until soft peaks form, 1 to 2 minutes. Transfer meringue to a medium bowl; set aside. Wipe mixer bowl clean.

Add castor sugar and butter to cleaned mixer bowl; beat with a stand mixer fitted with a paddle attachment on medium until creamy and fluffy, 3 to 4 minutes, stopping to scrape down sides as needed. Beat in vanilla, cinnamon, cloves, and the orange zest, about 10 seconds. Add egg yolks, one at time, beating until combined after each addition, about 30 seconds to 1 minute.

Stir baking soda into orange juice in a 2-cup measuring cup with a spout; whisk in milk and brandy until well combined.

With mixer on low, add flour mixture to butter mixture, alternating with orange juice mixture, ending with flour mixture and beating just until nearly combined, about 3 minutes. Fold in walnuts just until combined.

Gently fold meringue into batter in 3 additions.

Spread batter evenly in prepared baking pan. Insert 1 flouri into batter pan.

Bake the cake until a knife inserted into center comes out clean, 35 to 40 minutes. Let cake cool in pan on a wire rack for 15 minutes. Flip cake onto a wire rack. Remove and discard parchment paper. Allow cake to cool completely, about 2 hours. Trim cake flat using a serrated knife, if desired, and place cut side down on a serving platter. Dust generously with powdered sugar.