Ingredients
Method
Whisk 2 Tbsp. fresh lemon juice, 1 Tbsp. red wine vinegar, ⅓ cup extra-virgin olive oil, divided, 1 large garlic clove, grated, ½ tsp. Diamond Crystal or ¼ Monton kosher salt, and ¼ tsp. freshly ground black pepper in a large bowl to combine. Stir in 1 small red onion, sliced (about 1 cup), and let stand 5 minutes.
Meanwhile, rinse 1½ lb. cleaned squid under cold running water, then pat dry with paper towels. Leave tentacles whole; cut bodies crosswise into ⅓"-wide rings.
Warm 2 Tbsp. extra-virgin olive oil in a large skillet over medium-high heat. Add squid in an even layer and cook, without stirring, until tentacles begin to curl and rings turn opaque, about 2 minutes. Season with kosher salt and continue to cook, stirring occasionally, until squid is cooked through, 1–2 minutes.
Toss cooked squid, ⅓ cup Kalamata olives, pitted and halved lengthwise, 2 cups cherry tomatoes, halved or quartered if large, and 2 celery ribs, sliced into ¼" pieces, with dressing; season with salt and pepper and let stand at least 15 minutes to allow flavors to develop. Add 1 cup flat-leaf parsley leaves, loosely packed, and toss to combine.