1
Adjust rack to top position and preheat oven to 450 degrees. Wash and dry produce.
Halve, peel, and dice onion into ¾-inch-thick pieces; mince a few pieces until you have 2 TBSP (4 TBSP for 4 servings). Peel and mince or grate garlic (reserve a pinch for step 3). Zest and quarter lemon. Halve tomatoes lengthwise; scoop out and discard seeds with a spoon. Pat insides dry with paper towels. Finely chop parsley.