Broccoli-Stuffed Shells

Preheat oven to 350ºF. In small skillet, melt butter over medium heat. Add onion; cook until onion is tender but not browned. Remove from heat and let cool. In large bowl, stir ricotta cheese, egg, and seasoning mix, and stir until well-blended. Add broccoli and Jack cheese and mix well. In a large pot of salted boiling water, cook pasta shells 8 to 10 minutes or just until tender and drain. Rinse under cold running water and drain again. Stuff each shell with about 2 tablespoons broccoli-cheese mixture. In medium bowl, combine tomatoes, sautéed onion and salad dressing mix; mix well. Pour one-third of the tomato mixture into a 13 x 9-inch baking dish. Arrange filled shells in dish. Spoon remaining tomato mixture over top. Sprinkle with Parmesan cheese. Bake, covered, until hot and bubbly, about 30 minutes.