Imagine slicing into a warm, golden custard cake that trembles slightly on your spoon — creamy ricotta meeting bright lemon zest, with a delicate caramelized edge from the buttered skillet. This one-skillet Italian lemon ricotta custard cake is the kind of dessert that feels impossibly elegant for something so simple. Four eggs whipped with ricotta and cream cheese create a texture somewhere between a soufflé and a crustless cheesecake, while fresh lemon juice and vanilla bring that unmistakable Italian pasticceria charm. A scattering of toasted almonds on top adds the perfect golden crunch.

Every slice delivers 32 grams of fat and only 5 grams of net carbs, making this a textbook keto dessert that never feels like a compromise. The eggs and ricotta provide 16 grams of protein per serving, while erythritol handles the sweetness without a single gram of sugar. With fat accounting for nearly 78% of the calories, this custard cake keeps you firmly in ketosis while satisfying even the most persistent sweet tooth.

Best of all, this entire dessert comes together in one oven-safe skillet — you mix, pour, bake, and serve all from the same pan. It takes just 10 minutes of hands-on work before the oven does the rest. Serve it warm straight from the skillet for a weeknight treat, or chill it overnight for a denser, cheesecake-like texture that slices beautifully for company.

Ingredients (serves 4)

For the custard cake:

  • 4 large eggs, at room temperature
  • 1 cup (250g) whole milk ricotta cheese
  • 4 oz (113g) cream cheese, softened
  • 1/3 cup (53g) granulated erythritol or monk fruit sweetener blend
  • 2 tablespoons (14g) almond flour
  • Zest of 1 large lemon (about 1 tablespoon)
  • 2 tablespoons (30ml) fresh lemon juice
  • 1 teaspoon pure vanilla extract
  • 1/8 teaspoon fine sea salt

For the skillet and topping:

  • 2 tablespoons (28g) unsalted butter
  • 2 tablespoons (14g) sliced almonds
  • Powdered erythritol for dusting (optional)

Instructions

  1. Preheat your oven to 325°F (163°C). Place a rack in the center position. A lower temperature is key here — it ensures a silky, even set without cracking or browning too quickly on top.

  2. Prepare the skillet. Place a 9- or 10-inch (23–25cm) oven-safe skillet over medium-low heat. Add the butter and let it melt completely, swirling to coat the bottom and about an inch up the sides. Once the butter is melted and fragrant — about 1 minute — remove the skillet from the heat and set it aside. The residual warmth will keep the butter liquid while you make the batter.

  3. Beat the eggs and sweetener. In a large mixing bowl, whisk the eggs vigorously for about 30 seconds until slightly frothy. Add the erythritol and whisk for another minute until the mixture is smooth and the sweetener has mostly dissolved. You want a pale, slightly thickened base.

  4. Add the ricotta and cream cheese. Drop the softened cream cheese into the egg mixture in small pieces and whisk until no lumps remain. Add the ricotta and stir gently with a spatula or whisk until just combined — a few small curds of ricotta are perfectly fine and will create lovely pockets of creaminess as the cake bakes.

  5. Season the batter. Add the lemon zest, lemon juice, vanilla extract, almond flour, and salt. Fold everything together with a spatula until the batter is uniform. It should be pourable and look like a thick, creamy custard. Avoid over-mixing, which can deflate the eggs.

  6. Pour into the prepared skillet. Give the buttered skillet a final swirl, then pour the batter directly in. Use a spatula to gently smooth the top. Scatter the sliced almonds evenly across the surface — they will toast beautifully as the cake bakes, creating a golden crown.

  7. Bake for 22–28 minutes. The custard cake is done when the edges are set and lightly golden, the center has a very slight jiggle (like panna cotta, not like liquid), and a toothpick inserted near the center comes out with just a thin film of moisture. The top should be pale gold with toasted almonds. Do not overbake — the cake will continue to set as it cools.

  8. Rest before serving. Remove the skillet from the oven and place it on a wire rack or trivet. Let the custard cake rest for at least 10 minutes. It will deflate slightly from its puffed baked height — this is completely normal. Dust with powdered erythritol if desired, then slice into four wedges directly from the skillet.

Nutrition per Serving

Nutrient Amount
Calories ~370 kcal
Fat ~32g
Protein ~16g
Total Carbs ~6g
Fiber ~1g
Net Carbs ~5g

Nutrition is approximate and based on whole milk ricotta, full-fat cream cheese, and the stated ingredient quantities. Erythritol carbs are excluded as they have zero glycemic impact.

Tips & Variations

Choose your sweetener carefully. Granulated erythritol works best here because it dissolves cleanly into the custard. Avoid pure stevia drops unless you are experienced with dosing — too much creates a bitter aftertaste. If using a monk fruit–erythritol blend, use the same 1/3 cup measure. For a finer texture, pulse your erythritol in a blender for 10 seconds before adding it to the eggs; this prevents any graininess in the finished custard.

Make it ahead for a denser texture. This cake transforms beautifully overnight. Cover the cooled skillet tightly with plastic wrap and refrigerate for up to 3 days. Chilled, it becomes a dense, sliceable cheesecake with even more concentrated lemon flavor. Let it sit at room temperature for 15 minutes before serving, or enjoy it cold — both are wonderful.

Add an Italian mascarpone cream. For a more indulgent presentation, whip 1/4 cup (60g) mascarpone with 1 tablespoon heavy cream and a pinch of powdered erythritol until soft peaks form. Dollop on each warm slice. This adds roughly 60 extra calories and 6 grams of fat per serving while keeping net carbs virtually the same.

Swap the almonds to keep it nut-free. Replace the almond flour with an equal amount of coconut flour — just note that coconut flour is more absorbent, so the cake will be slightly denser. Swap sliced almonds for unsweetened coconut flakes or hulled hemp seeds for the topping. Both toast beautifully and keep the dish completely nut-free.

Watch for hidden carbs in ricotta. Not all ricotta is created equal on keto. Some commercial brands add stabilizers or milk solids that increase the carb count. Check the label and aim for ricotta with 3 grams of carbs or fewer per 1/4 cup serving. Whole milk ricotta from the deli section or Italian imports tend to be the cleanest. If you can only find part-skim, add an extra tablespoon of butter to the batter to keep the fat ratio on track.

Frequently Asked Questions

Will erythritol crystallize or get gritty as the cake cools?
Erythritol can sometimes recrystallize in cold desserts, creating a slightly grainy texture. In this recipe, the high moisture from the ricotta, eggs, and cream cheese helps keep it dissolved. If you are sensitive to this, use an allulose-based sweetener instead — allulose does not recrystallize and behaves almost identically to sugar in baked custards. Use the same volume measurement. Allulose does contain about 4 calories per gram but has a negligible glycemic impact, so it remains keto-friendly.
Can I substitute cottage cheese for the ricotta?
You can, but blend it first. Cottage cheese has a lumpier texture that will not melt into the custard as smoothly as ricotta. Pulse it in a blender or food processor for 20–30 seconds until completely smooth before adding it to the batter. Be aware that cottage cheese is typically slightly higher in protein and lower in fat than whole milk ricotta, so the final macro ratio will shift a bit. Adding an extra tablespoon of cream cheese can help compensate for the lower fat content.
How should I store and reheat leftovers?
Cover the skillet or transfer individual slices to an airtight container and refrigerate for up to 4 days. To reheat, place a slice on a microwave-safe plate and warm at 50% power for 30–45 seconds — just enough to take the chill off without making it rubbery. Alternatively, warm slices in a 300°F (150°C) oven for 8–10 minutes. This cake does not freeze well due to the high moisture content of the ricotta; thawed slices tend to weep liquid and lose their silky texture.
Can I make this dairy-free for vegan keto?
This recipe relies heavily on dairy for its texture, so a true vegan version would be a different dessert entirely. That said, you can get close by using cashew-based cream cheese (check carbs — some brands are higher), coconut cream in place of ricotta, and replacing the eggs with a flax egg and extra coconut cream for body. The texture will be more like a set pudding than a custard cake. For the butter, use refined coconut oil. Expect the macros to change significantly — always recalculate when making substitutions this substantial.
My cake puffed up dramatically then collapsed — did I do something wrong?
No, this is completely normal and actually a sign you whisked the eggs well. The eggs act as a natural leavener, trapping air that expands in the oven's heat. As the cake cools, that air contracts and the custard settles into its final, dense-creamy texture. If you prefer less dramatic rise and fall, whisk the eggs more gently and fold — rather than whisk — the ricotta in. A slightly lower oven temperature of 300°F (149°C) with a longer bake of 30–32 minutes will also produce a flatter, more even result.