Lemon Mug Cake

4.60 from 5 votes

This delicious lemon mug cake with lemon curd and glaze is absolutely amazing. It tastes like a lemon bar, in moist cake form.

Prep Time5

Cook Time4

Total Time9

Course: Dessert, Snack

Cuisine: American

Diet: Vegetarian

Servings: person

Calories: 132kcal

Cost: Recipe $0.82

1 egg yolk ($0.08)
2 tablespoons granulated sugar ($0.05)
2 tablespoons lemon juice ($0.12)
⅛ teaspoon salt ($0.01)
1 tablespoon unsalted butter, melted and cooled ($0.12)

4 tablespoons all-purpose flour ($0.03)
⅛ teaspoon salt ($0.01)
¼ teaspoon baking powder ($0.01)
2 tablespoons granulated sugar ($0.05)
3 tablespoons milk ($0.04)
1 tablespoon coconut oil, melted ($0.18)
1 tablespoon lemon juice ($0.06)
1 teaspoon lemon zest ($0.04)

Make the Lemon Curd: In a microwave safe bowl, whisk together the egg yolk, sugar, lemon juice, salt, and melted butter until smooth and the sugar is mostly dissolved.
Cook the Curd: Microwave for 2 to 3 minutes, stopping every 30 to 40 seconds to stir. Watch closely toward the end. The curd is done when it thickens and forms soft peaks on the back of a spoon. Remove immediately and allow to cool slightly or place in the freezer for a few minutes while preparing the cake.
Mix Dry Ingredients: In a microwave safe mug, stir together the flour, salt, and baking powder until evenly combined.
Add Wet Ingredients: Add the sugar, milk, coconut oil, lemon juice, and lemon zest. Stir until smooth. Small coconut oil bits from cold milk are fine.
Add the Curd: Spoon 1 tablespoon of the lemon curd over the top of the batter. Extra curd may be saved for another mug cake.
Microwave the Cake: Microwave for 1 minute 30 seconds to 2 minutes, depending on microwave strength. The top may look slightly wet. Use a fork to check the center if needed.
Make the Glaze: While the cake cooks, stir together the powdered sugar and water until smooth.
Finish & Serve: Spoon the glaze over the warm cake. Allow to cool slightly, then enjoy.

Microwave Timing: Microwave strength varies. Even a few extra seconds can affect both the curd and the cake, so watch closely.
Curd Safety: The egg yolk in the lemon curd should reach at least 160°F to be fully cooked, which typically occurs within about 2 minutes.
Texture Check: A slightly wet top is normal and will settle as the cake cools. Overcooking may result in a rubbery texture.
Oven Option: If using an oven safe mug, bake at 350°F for about 10 minutes on a baking sheet.
Juice Swap: Store bought lemon juice may be used if fresh lemons are unavailable. The flavor will vary slightly.