grilled lamb kebabs + tzatziki

INGREDIENTS

• 1 pound plain yogurt (regular or lowfat)
• 1/4 cup olive oil, plus more for brushing grill
• 1 teaspoon lemon zest
• 1/4 cup freshly squeezed lemon juice (2 lemons)
• 5 tablespoons fresh whole rosemary leaves, chopped
• 1 teaspoon kosher salt
• 1/2 teaspoon freshly ground black pepper
• 2 pounds top round lamb
• 1 red onion
• 14 ounces Greek yogurt (Ina recommends Fage Total; I recommend whatever you like best, and yes, I use full fat, always)
• 1 hothouse cucumber, unpeeled and seeded
• 1/4 cup sour cream
• 2 tablespoons freshly squeezed lemon juice
• 1 tablespoon white wine vinegar
• 1 tablespoon minced fresh dill
• 1 1/2 teaspoons minced garlic
• 2 teaspoons kosher salt