Preheat your oven to 350˚F. Spray an 18-by-13-inch half-sheet pan with nonstick baking spray that contains flour.

In a medium bowl, whisk together the all-purpose flour, baking powder, baking soda, and kosher salt.

In a large bowl, whisk the granulated sugar and eggs until foamy and lightened in color. Then whisk in the vegetable oil and vanilla extract.

Gradually add the flour mixture to the wet ingredients, alternating with the buttermilk, starting and ending with the flour mixture. Whisk well after each addition. Gently fold in the holiday sprinkles.

Pour the batter into the prepared sheet pan and smooth the top. Bake for about 20 minutes or until a toothpick inserted in the center comes out clean. Allow to cool completely in the pan for at least 1 hour before frosting.

Beat the salted butter on medium-high speed until light and fluffy. Reduce the speed to low, add half of the powdered sugar and mix until combined. Add the milk and vanilla extract, then add the remaining powdered sugar and mix until blended. Increase speed to medium-high and continue beating until fluffy and spreadable.

Spread about 3 cups of the buttercream uniformly over the cooled cake.

Transfer 1/4 cup of the remaining frosting into a piping bag with a small opening. Add forest green gel food coloring to the rest of the frosting until a deep green shade is achieved.

Mark a large triangle on the frosted cake for the Christmas tree’s body. Place 5 brown mini candy-coated chocolates per row in 3 rows for the tree trunk.

Pipe a row of 3/4-inch dots across the bottom of the triangle and drag each dot downward and outward to create branches. Continue piping dots for the entire triangle until covered.

Sprinkle holiday sprinkles around the cake border. Pipe small dots across the surrounding white icing to simulate snow.

Pipe swooping lines of white frosting across the tree for garlands. Press yellow mini candy-coated chocolates onto the white lines to resemble Christmas lights. Press red mini candy-coated chocolates onto the green branches as ornaments.

Cut the red sour candy belt lengthwise in half, fold one strip into a bow shape, and place it atop the tree.