Prepare the cake: Preheat the oven to 350°F (175°C). Grease and flour a 9×13-inch baking dish. In a medium bowl, whisk together the ground walnuts, flour, baking powder, cinnamon, cloves, and salt. Set aside. In a large bowl, beat the butter and sugar together until light and fluffy, about 3-4 minutes. Add the eggs one at a time, beating well after each addition. Stir in the oil, orange juice, orange zest, and vanilla extract. Gradually add the dry walnut mixture to the wet ingredients, mixing until just combined. Pour the batter into the prepared baking dish and smooth the top. Bake for 30-40 minutes or until a toothpick inserted into the center comes out clean. Let the cake cool in the pan for 10 minutes.

1. Make the syrup: In a saucepan, combine the water, sugar, lemon juice, and cinnamon stick (if using). Bring to a boil, then reduce the heat and simmer for 10 minutes. Remove from heat and stir in the vanilla extract. Set aside to cool.
2. Soak the cake: Once the cake has cooled slightly, poke holes all over the top with a skewer or fork. Pour the cooled syrup evenly over the cake, letting it soak in. Let the cake absorb the syrup and cool completely.
3. Serve: Once the cake has cooled and absorbed the syrup, cut it into squares or slices. Serve as a dessert with coffee or tea.