Take lamb out of fridge 1 hour before cooking.

Combine rosemary, garlic and olive oil and set aside.

Preheat oven to 220C fan forced.

Place lamb into oven tray, season with salt and pepper and baste with olive oil mix.  

Roast in the oven for 20 minutes, then turn down to 180C and roast for another 1  hour.  Baste with oil continually as it is cooking.

Remove from oven, the internal temperature should be 55-60C for medium rare.  Cover loosely with foil and rest for 20 minutes.

For the salad, tip the buckwheat into a large saucepan and dry-toast for 5 minutes, until golden brown and a nutty fragrance.  Remove from heat and let cool.

Tear the herbs into the buckwheat, season with salt, add 1 cup of lemon juice and oil, toss together and set aside.

Combine the yoghurt, remaining lemon juice, onion and sugar and season with salt and pepper.  Drizzle over the buckwheat to serve.