Pre-heat the oven to 350°F.
Season the chicken breast with garlic salt on both sides. Place the breasts in a bowl and add the cilantro and lime. Cut the onions and place on top. Toss it all together, mixing it in the cilantro and lime.
Coat a saute pan with oil (about a tablespoon). Once hot, place the chicken in it with the onions. You are going to sear the chicken on each side, to brown it. About 3-4 minutes on each side.
Once seared, place the chicken on a baking tray, and place in the oven for 8-10 minutes until the chicken is cooked all the way through, reaching an internal temperature of 165°F.
While the chicken is in the oven, finish cooking the onions on the stove, till they are translucent and soft.
Once the chicken is done, place on a plate with the onions on top and serve!