1. Preheat oven to 350°F (175°C). Grease and line one 8″, one 7″, two 6″, and two 4″ cake pans with parchment and nonstick spray.

2. In a large bowl, whisk flour, granulated sugar, brown sugar, baking powder, salt, cinnamon, ginger, and nutmeg until evenly combined.

3. On low speed, add unsalted butter and mix until no large chunks remain. Add eggs two at a time on low until just incorporated.

4. Mix in sour cream, applesauce, vegetable oil, and vanilla until just combined. Scrape down bowl, then beat on medium speed for 1 minute.

5. Divide batter into two portions. Add green gel food coloring — one light green, one darker green. Alternate spoonfuls into prepared pans to about 1″ high, then use an offset spatula to gently swirl batter for a marbled effect.

6. Bake 28–33 minutes or until a toothpick inserted in center comes out with a few moist crumbs. Cool in pans 10 minutes, then transfer to wire racks to cool completely. Level tops with serrated knife once cooled.

7. Stack cake layers from largest to smallest, trimming to form a tapered tree shape. Place on a greaseproof cake board and insert a wooden dowel or thick straw through center to stabilize.

8. For frosting: beat butter until smooth. Add vanilla and salt. Gradually add powdered sugar and heavy cream on low until combined. If too thick, add more cream; if too thin, more sugar. Chill briefly if needed.

9. Apply a thin crumb coat of buttercream to the stacked cake, smooth with offset spatula or bench scraper. Chill 30 minutes (or freeze 10 minutes) until firm.

10. Divide buttercream: reserve ½ cup white (pipe with small round tip), color ½ cup red (small French tip), ½ cup yellow (small round tip), remaining into light green and dark green (large open star tips).

11. Pipe green rosettes or stars all over cake for “branches.” Then pipe red, yellow, and white frosting dollops as ornaments. Chill 10 minutes to set frosting.