- 1 garlic clove, finely grated
- 5 tablespoons white wine vinegar
- 2 tablespoons chopped Peppadew peppers in brine
- 1 tablespoon mayonnaise
- 1 tablespoon sugar
- 1 1/2 teaspoons dried oregano
- 1/2 cup olive oil, plus more
- Kosher salt, freshly ground pepper
- 1 1/2 pounds skinless, boneless chicken thighs (about 6)
- 1 large sweet onion, sliced 1/2 inch thick
- 2 beefsteak tomatoes (about 1 pound), sliced 1/4 inch thick
- Oregano leaves and lemon wedges (for serving)
- Six to nine 8-inch metal skewers, or wooden skewers soaked 30 minutes in water
- Whisk garlic, vinegar, peppers, mayonnaise, sugar, dried oregano, and 1/2 cup oil in a medium bowl; season with salt and pepper. Transfer half of dressing to a small bowl; cover and chill until ready to serve.
- Cut chicken thighs lengthwise into long strips, about 1″–1 1/2″ wide (you should get 2–3 pieces per thigh). Combine chicken and remaining dressing in a large resealable plastic bag. Seal bag, pressing out any air. Turn to coat and chill at least 20 minutes and up to 1 day.
- Prepare a grill for medium-high heat; oil grate. Remove chicken from dressing; discard dressing. Thread 2 pieces of chicken onto each skewer. Season chicken lightly with salt and grill, turning occasionally, until golden brown and cooked through, 8–10 minutes.
- Meanwhile, drizzle onion with oil; season with salt. Grill until browned on both sides but still firm in center, about 3 minutes per side. Transfer to a large bowl and add tomatoes and a couple splashes of reserved dressing. Toss to coat; season salad with salt and pepper. Top salad and chicken with oregano leaves.
- Serve chicken with salad, reserved dressing, and lemon wedges for squeezing over.