1. Using a sharp knife, cut a 1/2" crosshatch pattern about 1/4" deep into lamb fat and meat. Mix together oil, garlic, salt, herbs, and spices in a bowl and rub all over lamb; let sit for 30 minutes to 1 hour.
2. Heat oven to 450 degrees. Place lamb (fat-side up) and lemons onto a wire rack set in a rimmed baking sheet and roast for 20 minutes.
3. Remove lemons and reserve for the sauce. Reduce oven temperature to 325 degrees and continue to roast lamb until center registers 130 degrees, 1 1/2 to 2 hours. Transfer lamb to a cutting board, tent with foil, and let rest for 30 minutes.
4. Squeeze juice from reserved roasted lemons into a small bowl; add basil, mayonnaise, creme fraiche, and mustard and whisk to combine. Slice lamb and serve with sauce.
Source: Hannaford fresh Magazine, March - April 2016