Combine 1/2 cup butter, green onions, and garlic in a 13- x 9- x 2-inch baking dish. Cover with heavy-duty plastic wrap, folding back a small section of wrap to allow steam to escape. Microwave at HIGH for 1 to 2 minutes or until butter melts and green onions are tender. Add shrimp and lemon juice, stirring to coat. Cover and microwave at HIGH for 4 minutes, stirring after 2 minutes. Stir in chopped dill. Cover and microwave at HIGH for 1 to 3 minutes or until shrimp turn pink. Let stand, covered, 1 minute. Stir in pimiento.
Combine hot cooked egg noodles, 2 tablespoons butter, salt, and pepper; stir until butter melts. Arrange seasoned noodles on a serving platter. Top with shrimp mixture. Garnish, if desired.