Quick drizzle icing for a simple chocolate cake

Easiest icing is ganache. Bring 3-4 ounces of heavy cream to a simmer. Pour it over 3-4 ounces (use equal amounts in weight) of chopped chocolate (or chocolate chips in a pinch). Whisk like crazy till it forms a dark liquid glaze. Use more chocolate if you want it thicker. You can flavor it with extract or zest, whatever you like.

Orange glaze -
3 tbsp orange juice, freshly squeezed if possible
1-2 tsp orange zest, chopped
1 tbsp olive oil
1 1/2 cups confectioner's sugar
Mix & drizzle over cake. If you want it thinner, add more orange juice, or water, by spoonfuls.