Preheat your oven to 450 degrees Fahrenheit. This high temperature is essential for a perfectly baked chicken that stays moist inside while developing a nice crust on the outside.
Drizzle 1 tablespoon of olive oil on both sides of the 2 ½ pounds of boneless skinless chicken breast. Make sure to cover it evenly to ensure juiciness while baking.
Season the chicken with salt and pepper to taste. This simple seasoning will enhance the overall flavor of your dish. Place the seasoned chicken in a 13 x 9 x 2-inch baking dish.
Bake the chicken in the preheated oven until it reaches an internal temperature of 165 degrees Fahrenheit. This should take about 15 to 18 minutes. The chicken should be golden and cooked through.
While the chicken is baking, prepare the pesto. In a resealable plastic bag, place 1 cup of packed basil and 1 cup of packed baby spinach. Use a rolling pin to gently bruise the herbs and greens. This helps release their natural oils and flavors.
Transfer the bruised herbs to a food processor or blender. Then, heat a medium-sized skillet over medium heat.
Toast the 3 cloves of unpeeled garlic in the skillet until the outsides are lightly browned, about 8 minutes. Keep shaking the pan occasionally to ensure even toasting.
Remove the garlic skins and add the garlic to the food processor with the herbs. This will add depth to your pesto.
In the same pan, place ¼ cup of walnuts and toast them over medium heat for about 3 to 4 minutes, stirring frequently to avoid burning. Transfer the toasted walnuts to the food processor.
Add ½ teaspoon of kosher salt and ¼ teaspoon of black pepper to the food processor. Pulse five times to begin breaking down the greens and nuts.
While the food processor is running on low speed, slowly drizzle in ½ cup of extra-virgin olive oil. This will create a smooth pesto mixture with some smaller pieces remaining.
After about 10 seconds, add ¼ cup of grated parmesan cheese to the pesto. Process on low speed for an additional 5 seconds. Taste the mixture and season with more salt and pepper as desired.
Once done, transfer the pesto to a small bowl. This sauce will be the perfect topping for your baked chicken.
After baking, brush some of the pesto sauce on each cooked chicken breast. Carefully transfer the chicken to a serving platter.
To finish, top the chicken with additional chopped walnuts and parmesan cheese, along with 1 cup of diced tomatoes for added color and flavor. Serve any remaining pesto sauce on the side for extra dipping!
