Heat oven to 375°F. Toss onions, sweet peppers and potatoes with oil and half the salt and pepper in large bowl. Spread in 13 x 9 x 2-inch baking dish.
Bake, uncovered, in 375°F oven for 40 minutes. Stir halfway through cooking.
After 40 minutes, add garlic, lemon juice, 1 can of tomatoes and hot sauce to baking dish; stir to combine.
Season fish with remaining salt and pepper. Cut into 6 servings. Arrange over top of potato mixture. Spoon remaining can of tomatoes over fish and vegetables.
Cover; bake another 30 minutes. Let covered baking dish stand 10 minutes before serving. Garnish with parsley.