In a saucepan, add olive oil, lemon juice, herbs, and onion and place over medium-low heat. Let come to a low boil and cook until the onions become translucent. Then add the garlic and sundried tomatoes along with some salt and pepper and cook for about 2-3 minutes. Remove from heat and let cool.
Place chicken in a baking dish then pour the cooled mixture on top. Cover and place in the fridge to marinate overnight.
Preheat oven to 375 degrees. Place marinated chicken on the baking sheet and scoop the onion and sundried tomato mixture on top then top the lemon slices on the chicken. Sprinkle with a little extra salt on top then place in the oven to bake for 30-35 minutes, or until internal temperature reaches 165 degrees F. This time will range depending on the thickness of the chicken breasts.
Let chicken rest for about 5 minutes before slicing.