Orange Olive Oil Snack Cake with Cocoa Ribbon

Steps

1. Preheat the oven to 350°F (175°C). Brush an 8-inch square pan with the canola oil and line it with parchment.
2. Make the dry mix: whisk the flour, baking powder, baking soda and salt in a bowl.
3. Make the cocoa filling: in a small bowl, stir together the unsweetened cocoa powder, brown sugar and chopped chocolate chips. Set aside.
4. In a large bowl, rub the lemon zest into the granulated sugar with your fingers until fragrant and damp.
5. Whisk the eggs into the zesty granulated sugar until pale, about 1 minute, then whisk in the olive oil, yogurt, vanilla and five-sixths of the orange juice, keeping the remaining one-sixth for the glaze.
6. Fold the dry mix into the wet mixture just until no dry streaks remain.
7. Spread half of the batter in the pan, sprinkle all of the cocoa filling evenly over it, then spoon the remaining half of the batter on top and gently smooth it to cover.
8. Bake 38 to 45 minutes, until a toothpick in the center comes out clean (a little melted chocolate is fine, but no wet batter).
9. Cool the cake in the pan on a rack for 20 minutes, then lift it out by the parchment and cool completely on the rack, about 1 hour.
10. Make the glaze: whisk the powdered sugar with the reserved one-sixth of the orange juice until smooth and pourable. Drizzle over the cooled cake, let it set 10 minutes, then cut into 12 slices.