How to Make It
Make the cake Preheat the oven to 350°. Grease an 8-inch springform pan with baking spray and line the bottom with parchment paper. Wrap the outside of the pan with foil and set on a rimmed baking sheet.
In a bowl, whisk the flour, cinnamon, baking powder, baking soda, salt, cloves, allspice and ginger. In another bowl, whisk the oil and honey. In a stand mixer fitted with the whisk, beat the eggs with both sugars at medium-high speed until thick and nearly doubled in volume, 4 minutes. Slowly beat in the oil-honey mixture until just combined, about 1 minute. (The batter will look broken but will emulsify.) In a measuring cup, combine the coffee, orange juice and vanilla paste. At low speed, beat the dry ingredients and the coffee mixture into the batter in 3 alternating additions, until just combined.
Scrape the batter into the prepared pan. Bake for about 55 minutes, until a toothpick inserted in the center comes out clean. Transfer the cake to a rack and let cool for 1 hour. Run a knife around the edge of the cake and remove the springform ring. Invert the cake and remove the springform bottom. Discard the parchment. Let the cake cool completely, about 45 minutes, then transfer to a large plate.
Meanwhile, make the frosting In a small saucepan, whisk 1/2 cup of the granulated sugar with the flour, then whisk in the milk. Bring to a boil over moderately low heat, whisking constantly, about 10 minutes. Scrape into a heatproof bowl and press a sheet of plastic wrap directly onto the surface. Let cool for 1 hour.
In a stand mixer fitted with the paddle, beat the butter with the remaining 1/2 cup of granulated sugar and the orange zest at medium speed until fluffy and smooth, about 5 minutes. Beat in the cooled flour mixture, 1 tablespoon at a time, beating well after each addition. Beat in the vanilla and salt and continue beating until smooth, about 2 minutes.
Spread a thin layer of frosting all over the cake and refrigerate until set, about 15 minutes. Spread the remaining frosting over the top and side of the cake. Refrigerate until the frosting is just firm, about 30 minutes. Top with candied orange slices before serving.
To make the candied orange slices, bring 1 1/2 cups water and 1/2 cup sugar to a boil. Add 1 navel orange (sliced 1/4 inch thick) and simmer for 30 minutes. Transfer the slices to a rack to cool.