Chop the rosemary and garlic into small pieces. Leave a few bunches of rosemary for decoration.
In a mixing bowl, combine 2 lbs of chicken breast, avocado oil, onion powder, paprika, salt, pepper, and arrowroot starch. Mix everything with hands until well combined. It should feel slightly floury on the outside of the chicken breast.
Grease a baking pan with avocado oil. Line up the chicken breast. Squeeze half a lemon on top.
Bake 450 F for 15 minutes, or until inner temperature reaches 160-165 F.
Let the roasted chicken sit for at least 10 minutes before cutting.
Notes
When baking at 450 F, I usually use this rule of thumb: 1 lb 7-8 minutes depending on thickness. See more tips on temperature when baking chicken breast in this post.
Make sure to have the chicken rest for 10+ minutes to soak the juice in before cutting.