Keto Cod Filet in Lemon Caper Butter with Green Beans
This keto cod filet relies on the beurre-noisette technique: butter is lightly browned in the pan, then capers and lemon juice are added to create a simple, aromatic sauce. Served with blanched green beans. The result: 52 g protein with 5 g net carbs, ready in 20 minutes.
Key facts at a glance
- Preparation time: approx. 20 minutes – 5 minutes prep, 15 minutes cooking.
- Approx. 5 g net carbs and 38 g fat per serving.
- Ingredients: cod filet (2 pieces), green beans, butter, capers, lemon, garlic, parsley.
- Suitable as a light keto dinner – best eaten fresh.
Ingredients
One serving equals two cod filets with sauce and green beans – intended as a complete keto dinner.
| Amount | Ingredient | Note | ||
|---|---|---|---|---|
| cod filet (skin-on) | 2 pieces, patted dry | |||
| 2 pieces, patted dry | ||||
| green beans | - | |||
| butter | - | |||
| capers (drained) | - | |||
| lemon | juice and thin slices for garnish | |||
| juice and thin slices for garnish | ||||
| garlic cloves | - | |||
| fresh parsley (chopped) | 1 tbsp | |||
| 1 tbsp | ||||
| olive oil | approx. 1 tbsp | |||
| approx. 1 tbsp | ||||
| salt | to taste | |||
| to taste | ||||
| pepper | to taste | |||
| to taste | ||||
Preparation
Pan-fry the cod filet skin-side down in olive oil, flip and finish cooking. Separately, brown the butter, then add capers and lemon juice. Blanch the green beans in parallel.
Why cod in caper butter fits keto well
Cod (Gadus morhua) is one of the leanest food fish: per 100 g only approx. 0.7 g fat with approx. 20 g protein. That makes it the purest protein source among fish. 350 g of cod filet therefore provide around 70 g protein with minimal intrinsic fat. The fat comes entirely from the caper butter sauce: 40 g butter delivers approx. 34 g fat, mostly saturated fatty acids and butter aroma. Capers (2 tbsp drained, approx. 20 g) are low in calories, have less than 0.5 g carbs and provide a salty, slightly bitter contrast. Green beans contain approx. 3 g net carbs per 200 g – ideal as a vegetable side. Lemon juice and parsley are negligible on the carb side. In total: approx. 52 g protein, 38 g fat, 5 g net carbs, approx. 560 kcal.
Source: USDA FoodData Central – Cod, Atlantic, cooked , FDDB Nutrition Database
Cod: The purest protein source among fish
Cod contains only approx. 0.7 g fat per 100 g but delivers approx. 20 g protein – a protein-to-fat ratio leaner than chicken breast. For keto this means: the fat has to be added through the cooking method (butter, oil) to reach the ketogenic macro profile. The butter sauce fulfills exactly this function while giving the dish its aromatic depth.
Beurre Noisette: Why browned butter tastes better
When butter is heated above 140 °C, the milk sugar caramelizes and the whey proteins react with the milk sugar (Maillard reaction) – this creates the nutty, caramel-like flavor of brown butter. For keto, browned butter is ideal: it contains the same macronutrients as regular butter but tastes more intense and you need less of it for the same flavor.
Source: Harvard T.H. Chan – The Nutrition Source: Fats and Cholesterol
How do I serve and vary the cod filet?
Place the cod filet on top of the beans and generously pour the caper butter over it. Garnish with fresh parsley and a lemon slice. From my own experience I recommend patting the cod filet very dry with paper towels before searing – moisture on the surface prevents browning and leaves the flesh steamed rather than crispy.
Fresh is better – using leftovers
Cod tastes best fresh and should be eaten right away. Leftovers (if any) can be served cold on a salad the next day – the caper butter sets in the fridge and can be used cold as a dressing. Reheating in the pan works but dries out the flesh.
Other white fish for this sauce
Tilapia, plaice or pollock work with the same technique. Plaice has a thinner texture and only needs 2 minutes per side. Pollock has slightly more inherent flavor but also pairs well with capers. For a fattier keto variant: swap cod for halibut (approx. 6 g fat/100 g).
Which tips help with the keto cod filet?
- Pat the cod filet very dry with paper towels before searing – browning only works on a dry surface.
- Sear skin-side first – the skin protects the delicate flesh and becomes crispy in the process.
- Only flip when the filet releases from the pan on its own – forced flipping tears the flesh.
- Add the butter for the sauce only after the cod is removed from the pan, then brown while swirling frequently – it burns quickly.
- Blanch green beans for 4 minutes and chill immediately in ice water – this keeps them bright green and crisp.
Nutrition values
| Nutrient | Per 100 g | Per serving | Keto context |
|---|---|---|---|
| Calories | approx. 165 kcal | approx. 560 kcal | Light keto dinner; the fat comes almost entirely from the caper butter, the cod itself is very lean. |
| Light keto dinner; the fat comes almost entirely from the caper butter, the cod itself is very lean. | |||
| Fat | approx. 11 g | approx. 38 g | Almost entirely from the brown butter; saturated and monounsaturated fatty acids – typical butter fat profile. |
| Almost entirely from the brown butter; saturated and monounsaturated fatty acids – typical butter fat profile. | |||
| Net carbs | approx. 1.5 g | approx. 5 g | Very low; comes from green beans and capers – well below the ketogenic daily limit. |
| Very low; comes from green beans and capers – well below the ketogenic daily limit. | |||
| Sugar | approx. 0.4 g | approx. 1.3 g | Natural sugar from green beans and lemon juice; no added sugar. |
| Natural sugar from green beans and lemon juice; no added sugar. | |||
| Protein | approx. 15 g | approx. 52 g | Very high; cod is one of the most protein-rich fish, complemented by butter protein. |
| Very high; cod is one of the most protein-rich fish, complemented by butter protein. | |||
| Salt | approx. 0.5 g | approx. 1.7 g | Moderate to high; mainly from the capers – drain capers well and don't add extra salt before searing. |
| Moderate to high; mainly from the capers – drain capers well and don't add extra salt before searing. | |||
Note: Nutrition values are estimated averages per 100 g and per serving and may vary depending on ingredients, brands, portion size, and preparation. They do not replace individual nutrition or medical advice.
FAQ
Is cod suitable for keto?
Yes, very much so. Cod is one of the leanest and lowest-calorie fish with only 0.7 g fat/100 g. Since keto requires a certain fat ratio, the fat has to be added during cooking (butter, oil) – which the caper butter sauce provides. This results in a fully keto-compliant profile.
Can I leave out or replace the capers?
Without capers the sauce becomes simpler but lower in carbs. As a substitute, olives (cut into small pieces) work well – similar salty contrast. Pickled cornichons add a sour note. If you like neither: simply use more lemon juice and fresh parsley for acidity and freshness.
How do I recognize fresh cod?
Fresh cod smells of the sea, not of fish. The flesh is pearly white to slightly grayish and springs back under light pressure. Good frozen product (without glaze) is often on par with fresh cod – thaw in the fridge overnight and pat dry well before searing.
Is this dish good for losing weight on keto?
Very much so: at 560 kcal and 52 g protein it is one of the lowest-calorie main courses. Cod itself has only approx. 90 kcal/100 g – the fat from the butter brings the calories. To reduce calories: cut butter to 25 g – then approx. 460 kcal.