- Prick unpeeled sweet potato several times with a fork. Microwave on high until tender, turning halfway through, 5 to 8 min. Let cool 20 min. Cut in half and scoop into a small bowl. Mash until smooth. Reserve 1/3 cup and set aside.
- Position rack in centre of oven, then preheat to 350F. Spray a 9×5-in. loaf pan with oil.
- Rub sugar and orange zest in a medium bowl with your hands to release the natural oils. Whisk in flour, baking powder and salt.
- Whisk eggs, oil, 1/3 cup reserved mashed sweet potato and orange juice in a large bowl. Stir in flour mixture until just combined. Scrape into prepared pan and smooth top. Bake until a tester inserted into centre of loaf comes out clean, covering with foil if top browns too quickly, 60 to 65 min. Allow loaf to cool for 10 min in pan. Remove to a rack to cool completely.
- Glaze: Whisk marmalade and lemon juice in a small bowl until smooth. Brush loaf with glaze, then decorate with candied clementines.
Kitchen Tip: To make candied clementines, thinly slice 3 clementines into 1/4-in. rounds. Remove any seeds. Boil 1/2 cup each water and granulated sugar in a large saucepan. Reduce heat to medium-low, then carefully add clementines. Simmer until slices look slightly translucent, about 20 min. Remove from heat, let cool in syrup before using.
Kitchen Tip: To make a round cake, increase canola oil to 1 cup. Pour batter into a parchment-lined 9-in. round baking pan. Reduce baking time to 50 min.