1. Marinate the lamb:
In a large bowl, whisk together the olive oil, lemon juice, garlic, salt, pepper, oregano, dill, and mint. Add the lamb and toss well to coat. Cover and refrigerate for at least 1 hour or up to overnight.   

2. Make the pickled red onions:
Combine the vinegar, water, sugar, and salt in a small saucepan and bring to a simmer, stirring until the sugar dissolves. Place the sliced onions in a heatproof bowl or jar and pour the hot brine over the top. Let sit for at least 30 minutes, then drain before serving.     

3. Roast the peppers & make the vinaigrette:
Char the bell peppers directly over a gas flame or under a broiler, turning occasionally, until blackened all over. Transfer to a bowl and cover for 10 minutes. Peel away the skins and remove the seeds.      Add the roasted peppers, red wine vinegar, lemon juice, garlic, and a pinch of salt and pepper to a blender. Blend until smooth. With the blender running, slowly drizzle in the olive oil until emulsified. Taste and adjust seasoning as needed.     

4. Grill the kebabs:
Preheat a grill or grill pan to medium-high heat. Thread the American lamb onto skewers. Grill for 10–12 minutes, turning occasionally, until nicely charred and cooked to your desired doneness. Let rest for 5 minutes before serving.   For medium-rare lamb, aim for an internal temperature of 130–135°F before resting.

5. Assemble & serve:
In a large bowl, toss the romaine, radicchio, tomatoes, cucumber, chickpeas, olives, feta, and scallions with a few spoonfuls of the vinaigrette. Spread onto a large serving platter. Remove the lamb from the skewers and arrange over the salad. Top with pickled onions, drizzle with more vinaigrette, and finish with fresh dill and mint.