Season chicken, if desired, with salt and pepper. Heat 1/2 tablespoon (7 mL) oil in large nonstick skillet over medium-high heat and cook chicken and onion, stirring frequently, until chicken is thoroughly cooked, about 4 minutes; remove and set aside.
Heat 1/2 tablespoon (7 mL) oil in same skillet over medium-high heat and cook half the carrots and squash, stirring occasionally, until vegetables are tender and golden around the edges, about 2 minutes. Remove vegetables and set aside. Repeat with remaining 1/2 tablespoon (7 mL) Oil and vegetables. Remove and set aside.
Prepare Knorr® Sidekicks® Fettuccine Alfredo Pasta Side Dish in same skillet according to package directions, stirring in spinach during last 1 minute of cook time. Stir in chicken, vegetables and lemon or lime juice. Garnish, if desired, with chopped fresh cilantro and lemon or lime wedges.