Roast leg of lamb with sweet onion marmalade

Food is central to the way in which we celebrate life, whether it marks a religious feast or a casual gathering with friends and family. Often what we share around the table is less important than the spirit in which it’s offered, although bringing a roast to the table is always special. Favoured for its distinctive taste, lamb lends itself well to a host of different cooking methods and flavourings. Simplicity is often the secret to the best recipes. Cooking doesn’t always need to be complicated. This roast leg of lamb with sweet onion marmalade is testament to the art of slow cooking.

Roast leg of lamb with sweet onion marmalade

Here, I’ve aimed to keep the ingredients to a minimum, using them in a way that concentrates the flavour of each. There are three key players in this recipe – succulent free-range Karoo lamb, red onions and Natura Sugars. When cooking with only a few ingredients, choosing the best quality is most important. I’m partnering with Natura Sugars, a Cape Town based company who’s exclusive range of unrefined sugars are truly superior. This special range of sugars are free from bleaching and irradiation. With 7 variants to choose from, they’ve become my go-to ingredient for baking and savoury meat dishes that require a sweet contrast.

Roast leg of lamb with sweet onion marmalade

The combination of savoury and sweet is a familiar to most South Africans. Fresh and dried fruits are mainstays to many local dishes, often popping up in lamb, chicken and beef recipes. Rather than the traditional use of fruit, I’ve chosen to caramelise heaps of onions with some garlic and thyme. A splash of balsamic vinegar helps gives the jam a tangy stickiness which I love. While the lamb and onions contain natural sugars, the addition of molasses-rich demerera sugar amps up the caramelisation.

Essential steps to making the Best Roast Leg of Lamb

There are essentially two steps to this lamb roast. Marinating and slow roasting. It’s as simple as that. I’m a firm believer in marinating, whether it’s a dry spice rub or an oil-based marinade. The meat benefits from an overnight resting, encouraging the flavours to draw deep into the lamb.  Let’s talk about cooking methods. Slow roasting gets the oven to do all the work. This is clever cooking. Once the prep work is done, it requires very effort, more of a watchful eye, really. Several hours later, you’re rewarded with meltingly tender meat and a pan-like jam that’ll impress the socks off your guests.

Roast leg of lamb with sweet onion marmalade

Roast leg of lamb with sweet onion marmalade
Roast leg of lamb with sweet onion marmalade
Serves 8


  • 2 tablespoons coriander seeds
  • 2 stems rosemary, de-stalked
  • 1 clove garlic, peeled
  • 2 red chilies, with or without seeds, depending on taste
  • 1 ½ teaspoons sea salt flakes
  • freshly ground black pepper
  • 1 tablespoon Natura Sugars Dark Demerara
  • 1/4 cup extra virgin olive oil

For the roast

  • extra virgin olive oil
  • 2.5kg free-range leg of lamb
  • 4 onions, peeled and cut into wedges
  • 1 whole garlic bulb, halved
  • 3 stems thyme
  • 1/4 cup chicken stock
  • 3 tablespoons Natura Sugars Dark Demerara
  • 2 tablespoons good quality balsamic vinegar
  • salt and cracked black pepper
  1. Starting with the marinade, toast the coriander seeds in a dry pan for several minutes until fragrant.
  2. Place all the marinade ingredients, except the olive oil in a spice grinder or mortar and pestle. Pulse or grind until fine. Combine the spices with the olive oil.
  3. Massage the spice marinade into the lamb, place in a non-metallic dish and cover with cling film. Refrigerate overnight.
  4. Remove the lamb from the fridge and bring up to room temperature. Preheat the oven to 180º C.
  5. Place the onions, garlic and thyme in a large roasting tin. Drizzle with olive oil and season with salt and pepper. Place the leg of lamb with the fatty side facing down on top of the onions. Pour the stock in around the sides of the roasting tin. Cover loosely with foil and roast for 2 ½ hours.
  6. Remove the foil and turn the lamb over. Add the Natura Sugars Dark Demerara and balsamic vinegar to onions and stir through to combine. Roast for a further 1 hour, uncovered. Turn the heat up to 220º C and cook for about 20 minutes.
  7. Remove the leg of lamb and garlic bulb halves from the roasting tin and cover with foil. Set aside to rest.
  8. Place the roasting tin with the onions on the hob. With the heat on high, reduce the pan juices until sticky. Add plenty of black pepper and adjust seasoning if necessary.
  9. Return the leg of lamb to the pan and heat through. Serve with root vegetable sides and rosemary roast potatoes.


Here are several more lamb recipes that are blog favourites:

Slow-roast lamb shawarma

North African Lamb knuckle bredie

North African Lamb Tagine with chickpeas and apricots



18 Comments. Leave new

  • This looks incredible! Want!

  • Dianne Bibby
    3 July 2016 8:54 am

    Thank you Kate. Loving the sweet and savoury combo!

  • I know I am probably an idiot – but when does the chicken stock go in?

  • Dianne Bibby
    19 July 2016 4:27 pm

    Hi Bryan. It seems I am! Apologies, you’re right. The stock goes in at the begging and is then reduced on the hob. I’ve corrected it on the blog. Thanks for the heads up.

  • I love the idea of a bit of sweet with the lamb. Thanks for a great idea. The black pepper is a nice touch too…

  • The sweet and savoury combination is hugely popular in our South African food culture, as is using flavoursome Karoo lamb. Thanks for stopping by.

  • Hi Dianne
    This looks truly amazing… Scrumptious… Just one question for you. I am hoping to cook 3 kg. Does the timing it temperature change if I cook more or less please.
    Thanks. Gilly

  • Super delicious! Made it for my family for Christmas, it was a huge success.
    Had the leftovers on mini bao buns as a snack, it was awesome (not that there was much leftover)

  • Dianne Bibby
    5 January 2018 3:52 pm

    Thanks Jolanda. I love trying new lamb roast recipes but I keep coming back to this one. I think it’s the sticky onion jam that does the trick.

  • Dianne Bibby
    5 January 2018 4:01 pm

    Hi Gilly. So sorry I’m only get to your question now. I’m sure you’ve already made it. Hopefully you went ahead and cooked it as per the recipe. It would’ve been perfectly fine. I often roast a larger joint and might add an extra 15 minutes to the overall cooking time.

  • We raise a small flock of sheep here in Montana so i’m always looking for some new cooking adventure with it. And now that i’ve made this i have a dilemma – I’ve always done lamb the old classic way with rosemary and olive oil. But I made this yesterday and LOVE LOVE LOVE it: which one shall i make next?

  • Ah, Joan. What a fabulous story!!! Food is quite endless, really. There are so many ways to skin a cat, as there are roasting lamb. This happens to be in our top three, too. The onion marmalade is just ridiculously good. The shawarma shanks come in at a pretty close second. All the best. Di

  • I did this for guests last weekend and it went down very well . I would definitely do it again. The sauce is delicious.

  • So happy to hear they loved it Marion. The sauce does give it wonderful flavour – sweet with just enough spice to counter the richness of the lamb. A happy festive season to you and your family.

  • great recipe…. made it yesterday but on a BBQ pit…. it was delicious… all the flavours… spicy…. sweet… yummy

  • Dianne Bibby
    17 May 2020 7:52 pm

    Sounds perfect, Sela. So glad you loved the flavours.

  • I’m going to roast my leg of lamb this way this Christmas

  • It’s one of the blog favourites every year, for both Christmas and Easter. A bankable recipe. x

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