Bring a large pot of water to boil and cook fettucini following manufacturers instructions on back of box. While pasta is cooking, heat olive oil in a large saute pan. Season chicken with salt and pepper and cook over medium to medium-high heat until cooked all the way through about 5 minutes each side. Remove from pan.
Dice chicken into pieces.
Turn heat to low and add onion and garlic. Saute for 3-4 minutes. Add a spash of white wine or water to saute pan and use a spatula to scrape any brown pieces on bottom of pan.
Return chicken to pan and add tomatoes. Cook 1-2 minutes.
Add cooked fettucini and pesto. Stir to heat through. Season with salt and pepper.Serve.