Melt 1/4 cup butter in large skillet over medium heat. When hot, add onions and saute until tender. Place half of onions in a 1 1/2 qt. deep-dish pie pan. Sprinkle 1 cup Swiss cheese and 1/2 cup cracker crumbs over onions. Repeat layers of onions and cheese. In a medium sized bow, beat eggs, milk, salt and pepper. Pout evenly over onion mixture. Melt 2 tablespoons butter in skillet over medium -high heat; stir in remaining cracker crumbs. Lightly brown, then sprinkle crumbs over casserole. Bake 25 minutes at 350 degrees. Good with beef or Ham.