Lemon potato cake is a moist, tender loaf cake that uses mashed potato to add richness and a soft, slightly dense crumb, with a bright lemon flavor from zest and juice. It is a clever way to use leftover potatoes and is popular in British and Irish baking, where it is often served with tea or as a simple dessert. The potato keeps the cake moist for days, and the lemon cuts through the sweetness perfectly.
Ingredients
- 1 cup (225 g) mashed potatoes, cooled (about 2 medium potatoes, boiled and mashed without butter or milk)
- 1 1/2 cups (190 g) all-purpose flour
- 2 tsp baking powder
- 1/2 tsp salt
- 3/4 cup (170 g) unsalted butter, softened
- 1 cup (200 g) granulated sugar
- 3 large eggs, at room temperature
- 1 tbsp lemon zest (from about 2 lemons)
- 2 tbsp fresh lemon juice
- 1 tsp vanilla extract
- 1/2 cup (120 ml) whole milk, at room temperature
For the Lemon Glaze (optional)
- 1 cup (120 g) powdered sugar
- 2–3 tbsp fresh lemon juice
Instructions
- Preheat your oven to 350°F (175°C). Grease a 9×5-inch (23×13 cm) loaf pan and line it with parchment paper, leaving some overhang on the long sides for easy removal.
- In a medium bowl, whisk together the flour, baking powder, and salt. Set aside.
- In a large bowl, beat the softened butter and sugar together with an electric mixer on medium speed until light and fluffy, about 2–3 minutes. Scrape down the sides as needed.
- Add the eggs one at a time, beating well after each addition. Beat in the lemon zest, lemon juice, and vanilla extract.
- Add the mashed potatoes and mix until combined. The mixture may look slightly curdled—that’s fine.
- With the mixer on low speed, add the flour mixture in three additions, alternating with the milk, starting and ending with the flour. Mix just until combined; do not overmix.
- Pour the batter into the prepared pan and smooth the top.
- Bake for 55–65 minutes, or until a toothpick inserted into the center comes out clean or with a few moist crumbs. If the top browns too quickly, loosely cover with foil after 40 minutes.
- Let the cake cool in the pan for 15 minutes, then lift it out using the parchment and transfer to a wire rack to cool completely.
- For the glaze, whisk together the powdered sugar and 2 tablespoons of lemon juice until smooth. Add more juice if needed for a drizzling consistency. Drizzle over the cooled cake and let set before slicing.
Tips
- Use dry mashed potatoes: Make sure your mashed potatoes are plain and not loaded with butter, milk, or cream. Excess moisture can make the cake heavy or gummy. If your potatoes are wet, pat them dry with a paper towel before measuring.
- Room temperature ingredients: Bring the eggs, milk, and butter to room temperature before starting. This helps the batter emulsify and creates a smoother, more even crumb.
- Don’t overmix: Once you add the flour, mix only until it disappears. Overmixing develops gluten, which can make the cake tough.
- Check for doneness: Ovens vary, so start checking the cake at 55 minutes. A toothpick inserted in the center should come out clean. If it has wet batter, bake for 5 more minutes and check again.
Serving Suggestions
Serve this lemon potato cake as a teatime treat, sliced and paired with a cup of Earl Grey or chamomile. It also makes a lovely dessert with a dollop of lightly sweetened whipped cream or a spoonful of lemon curd. For a brunch spread, offer it alongside fresh berries and a dusting of powdered sugar.
Variations
- Orange Potato Cake: Replace the lemon zest and juice with orange zest and juice for a sweeter, milder citrus flavor. Use orange juice in the glaze as well.
- Lemon-Poppy Seed: Add 2 tablespoons of poppy seeds to the dry ingredients for a classic crunch and nutty flavor.
- Gluten-Free: Substitute the all-purpose flour with a 1:1 gluten-free baking flour blend. The texture will be slightly more delicate, but the cake will still be moist.
- Herbed Version: For a savory twist, reduce the sugar to 1/2 cup, omit the vanilla, and add 1 tablespoon of fresh thyme leaves and 1 teaspoon of cracked black pepper. Skip the glaze and serve with soft cheese.
Storage and Reheating
Store the cake in an airtight container at room temperature for up to 3 days. It actually improves in flavor and moisture after a day. For longer storage, wrap the unfrosted cake tightly in plastic wrap and then foil, and freeze for up to 3 months. Thaw overnight in the refrigerator and bring to room temperature before serving. To reheat individual slices, microwave for 10–15 seconds or warm in a toaster oven at 300°F (150°C) for 5 minutes.
Frequently Asked Questions
Can I use instant mashed potatoes? Yes, you can, but prepare them according to the package directions without adding extra butter or milk. Let them cool completely before using. The texture may be slightly different, but it will still work.
Why did my cake sink in the middle? This can happen if the batter is overmixed, which develops too much gluten, or if the oven temperature is too low. Make sure your oven is properly calibrated, and avoid opening the oven door during the first 40 minutes of baking.
Can I make this cake without a mixer? Absolutely. Use a wooden spoon and a bit of elbow grease. Beat the butter and sugar until light and fluffy, then stir in the eggs and other wet ingredients. Just be extra careful not to overmix when adding the flour.
Can I reduce the sugar? You can reduce it to 3/4 cup (150 g) without affecting the structure too much, but the cake will be less sweet and the lemon will be more pronounced. The glaze also adds sweetness, so you could omit it for a less sweet version.
Do I need to peel the potatoes before boiling? It’s easier to peel them before boiling, but you can also boil them with the skin on and then peel them while warm—the skins slip off more easily. Just make sure to mash them thoroughly until no lumps remain.
Can I use sweet potatoes instead? Yes, sweet potatoes work well and give a slightly denser, more earthy cake. Use the same amount, and consider adding a pinch of cinnamon or nutmeg to complement the sweetness.
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