Preparation Preheat oven to 500°F. Cut potatoes into 1/2-inch-thick slices and toss with garlic, onions, oil, salt, and pepper in skillet (or roasting pan). Roast in middle of oven until potatoes begin to brown, about 15 minutes. Add tomatoes, tossing to combine, and roast until skins wrinkle and split, about 10 minutes. Add clams and red pepper flakes and roast, covered with lid (or tightly covered with foil), until clams are fully open, 6 to 10 minutes. (Discard any clams that have not opened after 10 minutes.) Sprinkle with parsley and serve in skillet.
Preparation Preheat oven to 500°F. Cut potatoes into 1/2-inch-thick slices and toss with garlic, onions, oil, salt, and pepper in skillet (or roasting pan). Roast in middle of oven until potatoes begin to brown, about 15 minutes. Add tomatoes, tossing to combine, and roast until skins wrinkle and split, about 10 minutes. Add clams and red pepper flakes and roast, covered with lid (or tightly covered with foil), until clams are fully open, 6 to 10 minutes. (Discard any clams that have not opened after 10 minutes.) Sprinkle with parsley and serve in skillet.