Keto Baked Cod with Herb Butter

This keto baked cod is cooked “en papillote,” sealed in a parchment parcel with ribbons of zucchini, cherry tomatoes and a slice of garlic, lemon and herb butter. As the parcel bakes, the butter melts and the fish steams in its own juices, so it comes out moist and fragrant every time. It takes about 30 minutes, serves 2, and has about 29 g of protein and roughly 5 g of net carbs per parcel. Add a few prawns or a langoustine to each parcel, as in our photo, for a seafood dinner.

• Serves: 2
• Prep time: 15 minutes
• Cook time: 15 minutes
• Total time: about 30 minutes

Ingredients

Herb butter

• 20 g (1½ tablespoons) softened butter
• 1 small garlic clove, grated
• 1 tablespoon finely chopped parsley
• 1 tablespoon snipped chives
• Finely grated zest of ½ lemon
• A pinch of salt and black pepper

Parcels

• 2 thick cod fillets, about 150 g (5 oz) each, skinless
• 1 medium zucchini (about 200 g), cut into thin ribbons with a peeler
• 100 g (⅔ cup) cherry tomatoes, halved
• 2 teaspoons lemon juice, plus wedges to serve
• 1 garlic clove, thinly sliced
• 4 to 6 raw peeled prawns or 2 langoustines (optional)
• 2 large sheets of baking parchment, about 40 cm (16 inches) square

Method

1. Heat the oven to 200°C (400°F), or 180°C (350°F) with the fan on.
2. Mash the soft butter with the grated garlic, parsley, chives, lemon zest, salt and pepper. Shape it into a small log on a piece of cling film or parchment and chill it while you make the parcels.
3. Fold each parchment sheet in half to make a crease, then open it out flat.
4. Pile half the zucchini ribbons, tomatoes and sliced garlic next to the crease on each sheet.
5. Set a cod fillet on top of each pile, season lightly, and add the prawns or langoustine, if using. Sprinkle a teaspoon of lemon juice over each.
6. Cut the herb butter into slices and lay them over the fish.
7. Fold the parchment over the fish, then fold and crimp the open edges tightly in small overlapping pleats to seal the parcel, leaving some air space inside.
8. Put the parcels on a baking tray and bake for 12 to 15 minutes, until the cod is opaque all the way through and flakes when pressed. If you’re unsure, open one parcel and check: fish should reach 63°C (145°F), as the FDA advises, and prawns should be pink and firm.
9. Serve the parcels at the table and cut them open carefully, as hot steam will escape. Spoon the buttery juices over the fish.

Tips for perfect parcels

• Seal them well. Tight folds trap the steam that cooks the fish. Foil works if you don’t have parchment.
• Cut vegetables thinly so they cook in the same time as the fish. Peeler ribbons, thin slices and halved cherry tomatoes are ideal.
• Use thick fillets. Thin pieces of fish overcook before the vegetables are done.
• Make extra herb butter. It keeps in the fridge for a week or the freezer for 3 months, and it’s great on steak, vegetables or eggs.
• Open one parcel to check rather than guessing; reseal and return it to the oven if it needs longer.

Swaps and variations

• Other fish: haddock, hake, sea bass, salmon or trout. Salmon may need 2 to 3 extra minutes.
• Other vegetables: thin asparagus, spinach, fennel slices, mushrooms or green beans.
• Mediterranean: add olives, capers and a sprig of oregano.
• Asian-style: swap the butter for a little sesame oil, ginger, garlic and soy sauce, with spring onions and bok choy.
• Dairy-free: use olive oil mixed with the herbs instead of butter.
• Not on keto? Serve with new potatoes or crusty bread to soak up the juices.

Nutrition per serving (estimate)

One serving is one parcel without the optional prawns. These figures were calculated from USDA FoodData Central values for raw Atlantic cod, unsalted butter, garlic, parsley, chives, lemon juice, zucchini, cherry tomatoes and salt. Prawns add about 12 g of protein, 50 calories and no carbs per 60 g.

Cod is a very lean white fish, so most of the fat here comes from the herb butter, which keeps the dish light enough to pair with a richer side. Cod is in the FDA’s “best choices” group for low mercury, and it provides iodine, selenium and vitamin B12. Our guide to seafood on keto covers other fish and shellfish, and our guide to healthy fats on keto explains how to balance butter with olive oil and oily fish.

Contains: fish and milk (butter). Shellfish, if you add prawns or langoustine.

Storage

Parcels are best eaten as soon as they’re cooked. Leftover cod can be cooled, refrigerated within 2 hours and eaten within 2 days, cold in a salad or gently reheated until hot all the way through. Assembled, uncooked parcels can be kept in the fridge for a few hours before baking; add 1 to 2 minutes to the cooking time.

What to serve with it

• Our creamy keto cauliflower mash.
• A crisp green salad with one of our keto salad dressings.
• Steamed green beans or broccoli tossed in a little of the herb butter.

Common questions

What does “en papillote” mean?

It’s French for “in paper.” The food is sealed in a parchment parcel and baked, so it steams in its own juices.

Can I use frozen cod?

Yes. Thaw it overnight in the fridge and pat it dry before making the parcels. If cooking from frozen, add 5 to 8 minutes and check that it’s cooked through.

Is butter keto?

Yes. It has almost no carbs, but it’s high in saturated fat, so use it in moderate amounts and include unsaturated fats such as olive oil, nuts and avocado too.

Safety note: Keto isn’t suitable for everyone. If you have diabetes, kidney or liver disease, take regular medication, or are pregnant or breastfeeding, talk to your doctor before cutting carbs this far (why it matters).

This article is general information, not medical advice. Nutrition figures are estimates from USDA FoodData Central and will change with the brands and amounts you use. If you follow a diet for a medical reason, check the recipe with your doctor or dietitian.