June 4, 2026 · Yavelle Recipes · 6 min read
Fajitas are a natural fit for a low-deuterium diet. The base of the dish — good quality beef, vegetables and spices — is already made up of foods that sit at the lower end of the deuterium range. A few targeted upgrades are all it takes to turn a great keto dinner into a genuinely low-deuterium meal.
| Prep Time | 10 minutes | Cook Time | 25 minutes |
| Servings | 4 | Net Carbs | ~7g per serving |
The Low Deuterium Ingredient Swaps
The original keto fajita recipe is already a strong low-carb foundation. These four upgrades take it firmly into low-deuterium territory without changing the character of the dish at all.
| Original Ingredient | Low Deuterium Swap | Why |
|---|---|---|
| Standard flank steak | Grass-fed flank steak | Beef is a fat-and-protein food with no sugar or starch, and is naturally low in deuterium |
| Olive oil | Grass-fed ghee | Ghee is almost entirely fat with negligible water content, and is naturally low in deuterium. It also has a high smoke point, perfect for the high heat needed to char steak and vegetables properly |
| Mixed red, yellow and green bell peppers | Primarily green bell peppers | Green peppers are less ripe and contain less natural sugar than red or yellow varieties — while still delivering great flavour and char |
| No specified topping | Fresh guacamole + grass-fed sour cream | Avocado is naturally low in deuterium — very high in fat, very low in sugar. Grass-fed sour cream adds more fat from a pasture-raised source |
Ingredients
Steak & Vegetables
- 1½ lb grass-fed flank steak
- 3 green bell peppers, thinly sliced
- 1 red bell pepper, thinly sliced (for colour)
- 1 large onion, thinly sliced
- 2 tbsp grass-fed ghee, divided
- 2 tsp pink Himalayan salt
- 1 tsp black pepper
- 1 tsp cumin
- 1 tsp paprika
- 1 tsp garlic powder
- ½ tsp chilli powder
Low Deuterium Toppings
- 2 ripe avocados, mashed into guacamole with lime juice and salt
- Grass-fed sour cream
- Fresh coriander (cilantro)
- Lime wedges
- Sugar-free salsa (optional)
Instructions
- Heat your pans. Place two cast iron skillets or heavy-bottomed pans over high heat. Add 1 tablespoon of grass-fed ghee to each and allow to heat until shimmering. You want them very hot before anything goes in — this is what creates that essential char.
- Cook the peppers and onions. Add the sliced green and red peppers, onion, cumin, paprika, garlic powder, chilli powder, and half the salt and pepper to the first skillet. Toss to coat in the ghee and leave on high heat, stirring occasionally, until the edges start to blacken and char. Once charred, reduce heat to medium and cook until just tender. Remove from heat and set aside.
- Slice the steak. Using a sharp knife, slice the grass-fed flank steak into thin strips, cutting against the grain — this shortens the muscle fibres and keeps the meat tender. Season generously with the remaining salt and pepper.
- Sear the steak. Add the sliced steak to the second hot skillet in a single layer. Don't stir immediately — let it sear for 1–2 minutes to develop colour. Cook to your preference, keeping in mind that thin strips cook quickly. Medium-rare to medium is ideal for flank steak — it becomes tough if overcooked.
- Combine and finish. Once the steak is cooked to your liking, add the charred peppers and onions back in and toss everything together over high heat for 30 seconds. Remove from heat immediately.
- Make the guacamole. Mash the ripe avocados with a generous squeeze of lime juice, a pinch of salt, and cracked pepper. Keep it chunky for the best texture.
- Serve. Spoon the steak and pepper mixture over cauliflower rice or into crisp lettuce cups. Top generously with guacamole, grass-fed sour cream, fresh coriander, and a wedge of lime on the side.
Why Grass-Fed Beef Is the Star of This Recipe
Plenty of cooks prefer the flavour, and beef of any kind is a fat-and-protein food with no sugar or starch in it.
Flank steak is an ideal cut for fajitas because it's lean, absorbs seasoning brilliantly, and — when sliced correctly against the grain — is remarkably tender.
Serving Suggestions
Cauliflower rice is the natural base for a low-deuterium fajita bowl — it soaks up the spiced juices from the steak and is very low in deuterium. For a lighter option, large crisp iceberg or romaine lettuce leaves make excellent wraps and add a satisfying crunch. If you want to keep the traditional fajita feel, look for low-carb tortillas made from almond or coconut flour.
For toppings, prioritise avocado in any form — sliced, mashed or made into a proper guacamole. Grass-fed sour cream, grated grass-fed cheddar, and fresh lime juice all add fat, flavour and low-deuterium credentials in one go.
Storage
The steak and pepper mixture keeps well in an airtight container in the fridge for up to 3 days. Reheat quickly in a hot skillet with a small knob of ghee — this revives the char and keeps the texture far better than a microwave. Make guacamole fresh each time, as avocado browns quickly once mashed. The spice blend used in this recipe can be made in bulk and stored in a jar — it's a great all-purpose seasoning for any low-deuterium beef or chicken dish.
Nutrition Per Serving
| Nutrient | Amount (estimated) |
|---|---|
| Calories | ~320 kcal |
| Fat | 18g |
| Protein | 30g |
| Total Carbs | 10g |
| Fibre | 3g |
| Net Carbs | ~7g |
Nutrition is estimated and will vary based on exact ingredients and toppings used.
Frequently Asked Questions
Can I use a different cut of beef?
Yes. Skirt steak is the most traditional choice for fajitas and works just as well — slice against the grain as you would with flank. Sirloin or ribeye strips are also excellent and slightly more forgiving to cook. Whatever cut you choose, opt for grass-fed if you can.
Can I make this with chicken instead of beef?
Absolutely. Use pasture-raised chicken thighs cut into strips and cook over medium-high heat until just cooked through. The spice blend works beautifully with chicken. See our Low Deuterium Kung Pao Chicken and Chicken Cordon Bleu posts for more on sourcing pasture-raised poultry.
Are onions low in deuterium?
Onions contain more natural sugar than the other vegetables in this dish. In the amount used here — spread across four servings — they contribute a great deal of flavour for very little carbohydrate. If you want to keep the sugar lower still, reduce the onion to half a portion or replace it with spring onions.
Is sour cream low in deuterium?
Full-fat, grass-fed sour cream is a good low-deuterium topping. It's high in fat and low in sugar.
Where does this recipe fit in the Yavelle low deuterium series?
This is part of our ongoing low deuterium recipe series, where we take well-loved dishes and adapt them to ingredients that are naturally low in deuterium, without sacrificing flavour or satisfaction. Browse the full series on the Yavelle blog for more recipes just like this one.
Yavelle 25ppm Deuterium-Depleted Water is a packaged food. It is not a therapeutic good and is not intended to diagnose, treat, cure or prevent any disease. Information on this page is general and is not medical advice. If you have a health condition or are undergoing treatment, speak with a qualified health practitioner.