Keto Lamb Filet with Herb Butter and Green Asparagus
This keto lamb filet from the loin is seared briefly in a cast-iron pan, topped with homemade herb butter and served with green asparagus. The serving delivers 50 g protein and 45 g fat at only 3 g net carbs in 20 minutes, an elegant weekend dinner.
Key facts at a glance
- Total time: approx. 20 minutes, 5 minutes prep, 12 minutes pan, 3 minutes resting.
- Approx. 3 g net carbs and 45 g fat per serving.
- Ingredients: lamb filet, butter, garlic, parsley, thyme, lemon zest, green asparagus, olive oil.
- Great as a summery keto dinner during asparagus season or as a refined weekend meal.
Ingredients
One serving equals 200 g lamb filet with 25 g herb butter and 150 g green asparagus, designed as a complete main course.
| Amount | Ingredient | Note | ||
|---|---|---|---|---|
| Lamb filet | 2 pieces of 200 g each | |||
| 2 pieces of 200 g each | ||||
| Butter (for herb butter) | softened | |||
| softened | ||||
| Garlic cloves | 1 finely chopped for the butter, 1 lightly crushed for basting | |||
| 1 finely chopped for the butter, 1 lightly crushed for basting | ||||
| Fresh parsley | approx. 2 tbsp chopped | |||
| approx. 2 tbsp chopped | ||||
| Fresh thyme | approx. 1 tsp | |||
| approx. 1 tsp | ||||
| Lemon zest | grated zest of 1 organic lemon | |||
| grated zest of 1 organic lemon | ||||
| Green asparagus | bottom third peeled, woody ends trimmed | |||
| bottom third peeled, woody ends trimmed | ||||
| Olive oil | approx. 1.5 tbsp | |||
| approx. 1.5 tbsp | ||||
| Salt | to taste | |||
| to taste | ||||
| Pepper | to taste | |||
| to taste | ||||
Preparation
Sear the lamb filet hard, baste with butter and garlic, then rest. In parallel, briefly pan-fry the asparagus in a second skillet and plate it with the herb butter on top of the filet.
Why this dish fits keto well
Lamb filet from the loin is one of the most tender and leanest lamb cuts (approx. 22 g protein, 12 g fat per 100 g). 200 g of lamb filet per serving deliver around 44 g protein and 24 g fat from the meat alone. The herb butter (25 g per serving) adds another 20 g of fat without notable carbs. Green asparagus is very keto-friendly at approx. 2 g net carbs per 100 g; 150 g per serving contribute around 3 g net carbs. Olive oil for searing and garlic in moderate amounts are nutritionally unproblematic. Overall, the serving comes to approx. 3 g net carbs, 45 g fat and 50 g protein at around 600 kcal.
Source: USDA FoodData Central, Lamb, loin, raw , Harvard T.H. Chan, The Nutrition Source: Vegetables and Fruits
Green asparagus as a keto side
Green asparagus has one of the best profiles among spring vegetables at approx. 2 g net carbs per 100 g. It also provides folate and vitamin K and is filling thanks to its fiber. White asparagus has similar macros but needs a longer cooking time and is classically boiled in water, while green asparagus pairs much better with quickly cooked meat straight from the pan.
Source: USDA, Asparagus, green, raw
Homemade herb butter: high in fat, no additives
Homemade herb butter from soft butter with parsley, thyme, garlic and lemon zest contains no starches or added sugars. 25 g per serving deliver around 20 g fat and under 0.5 g carbs. Store-bought herb butter sometimes contains maltodextrin or sugar, so check the label or, better, make your own.
How do I serve and vary the lamb filet?
Place the lamb filet on a preheated plate, top with a thick slice of herb butter and serve immediately, the butter will melt at the table over the warm meat. From personal experience, it pays off to take the lamb filet out of the fridge 20 minutes before searing so the core temperature comes up properly during the short cooking time.
Meal prep: prepare ahead and reheating
The herb butter keeps for up to 5 days in the fridge or 3 months frozen, ideally shaped into a roll and sliced into portions. Lamb filet should be cooked fresh and not reheated, otherwise it turns tough. Cooked asparagus keeps for 2 days in the fridge and can go cold into a salad bowl.
Out of asparagus season
Outside asparagus season (April to June), green beans (4 g net carbs per 100 g), broccoli florets (3 g net carbs per 100 g) or bok choy (2 g net carbs per 100 g) are good alternatives. All three pan-fry just as quickly and pair well in flavor with lamb and herb butter.
Which tips help with keto lamb filet and herb butter?
- Take the lamb filet out of the fridge 20 minutes before searing, room temperature ensures even cooking.
- Let the pan get truly smoking hot before adding the meat, otherwise you will not get a crust.
- Sear the filet on all 4 sides for 1 minute each, then baste for 2 to 3 minutes, target 56 °C / 133 °F for medium-rare.
- Mix the herb butter at least 30 minutes before cooking so the flavors meld.
- Pan-fry the asparagus in the same pan after the meat, the lamb fat adds extra flavor.
Nutrition values
| Nutrient | Per 100 g | Per serving | Keto rating |
|---|---|---|---|
| Calories | approx. 160 kcal | approx. 600 kcal | Complete main course; energy from lamb filet, butter and olive oil. |
| Complete main course; energy from lamb filet, butter and olive oil. | |||
| Fat | approx. 12 g | approx. 45 g | Saturated from butter, monounsaturated from olive oil, an ideal ketogenic split. |
| Saturated from butter, monounsaturated from olive oil, an ideal ketogenic split. | |||
| Net carbs | approx. 0.8 g | approx. 3 g | Very low; almost entirely from the asparagus. |
| Very low; almost entirely from the asparagus. | |||
| Sugar | approx. 0.5 g | approx. 1.5 g | Very low; natural sugars from asparagus. |
| Very low; natural sugars from asparagus. | |||
| Protein | approx. 13 g | approx. 50 g | Very high; covers about 33 % of the daily protein needs of a 75 kg person. |
| Very high; covers about 33 % of the daily protein needs of a 75 kg person. | |||
| Salt | approx. 0.3 g | approx. 1 g | Moderate; butter is usually salted, so season carefully at the end. |
| Moderate; butter is usually salted, so season carefully at the end. | |||
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
What is the difference between lamb filet and lamb loin?
The lamb filet is the narrow, cylindrical tenderloin that sits inside the lamb loin, the most tender cut. The lamb loin is the whole back strip including the filet; once trimmed out, each animal yields only about 200 to 300 g of pure filet. Both have similar macros, the filet is just much smaller and more expensive.
What is the right core temperature for lamb filet?
56 °C / 133 °F for medium-rare (pink and juicy inside), 60 to 62 °C / 140 to 144 °F for medium. Above 65 °C / 149 °F the filet turns tough, it is significantly leaner than lamb chops and does not tolerate overcooking. Use a meat thermometer or the finger test: springy-firm means medium-rare.
Can I use frozen lamb filet?
Yes, but thaw it slowly in the fridge overnight, not in the microwave, otherwise the filet loses juices. Patting it dry before searing is especially important with thawed meat, since it releases more liquid and would otherwise fail to develop a crust.
Does this dish fit keto for weight loss?
Yes, very well: 50 g of protein keep you full for a long time, and the low carb count (3 g) leaves plenty of room in your daily budget. To cut calories, you can drop the herb butter to 15 g and halve the asparagus olive oil to 5 g, the serving then drops to about 480 kcal while still delivering 48 g of protein.