Chocolate Orange Spiderweb Sheet Cake

Ingredients

• 1 3/4 cups all-purpose flour (220 g)
• 3/4 cup natural cocoa powder (65 g)
• 1 1/2 teaspoons baking soda (7 g)
• 1 teaspoon baking powder (4 g)
• 1/2 teaspoon salt (3 g)
• 2 eggs (100 g)
• 1 cup buttermilk (240 g)
• 1/2 cup oil (110 g)
• 2 teaspoons vanilla and orange zest (16 g)
• 1/4 cup orange juice, divided (60 g)
• 1 cup butter, softened (227 g)
• 3 1/2 cups powdered sugar (420 g)
• orange and black gel coloring (4 g)

Instructions

1. Prepare pan. Heat oven to 350°F. Grease a 9-by-13-inch metal pan, line with parchment leaving long handles, and grease parchment. Set pan on a rimmed baking sheet if it feels thin or flexible.
2. Whisk dry ingredients. Whisk flour, cocoa, baking soda, baking powder, and salt in a large bowl until evenly colored. Add granulated sugar and whisk again, breaking apart visible cocoa lumps with your fingers.
3. Mix batter. Make a well. Add eggs, buttermilk, oil, vanilla, orange zest, and two tablespoons of orange juice. Whisk from the center outward only until no flour streaks remain and the batter looks fluid.
4. Bake cake. Pour batter into pan and tap twice on counter. Bake 26 to 30 minutes, until a toothpick near center has a few moist crumbs. Cool in pan 20 minutes, then lift cake to a rack and cool completely.
5. Make orange frosting. Beat butter smooth. Add powdered sugar, remaining orange juice, and orange gel coloring in stages, beating after each addition until fluffy. Spread frosting over the completely cool cake, smoothing it level with an offset spatula.
6. Pipe and cut. Tint a small portion of frosting black and spoon it into a zip-top bag. Snip a tiny corner, pipe a spiral from center outward, then drag a toothpick outward at intervals. Chill 15 minutes if needed, then cut into squares.

Notes

• Use the same orange juice for batter and frosting, but measure the frosting portion after zesting and juicing. If frosting seems loose, beat in powdered sugar one tablespoon at a time until it spreads without running over the edges.
• A tiny bag opening matters: start smaller than you think, because widening the snip is easy but narrowing it is not.