Season pounded chicken breasts with salt and pepper; dredge in flour. In a skillet, heat a drizzle EVOO over high. Add chicken; cook until golden brown on both sides and cooked through, about 3 minutes per side. Transfer to a plate. Add a tablespoon minced shallot to the pan; stir 30 seconds. Add water or stock and the grapefruit juice. Stir, scraping up browned bits, and cook until sauce thickens. Off heat; whisk in cold butter. Add tarragon. Season. Spoon the sauce over the chicken.
How To Make Pan Sauce