Melt the butter in an ovenproof skillet over medium-high heat, and brown the chicken breasts about 3 minutes on each side. Remove chicken from the skillet, and set aside. Add the onion and asparagus to the skillet; cook for 4 to 5 minutes, or until the onions are tender. Arrange the chicken breasts over the onions and asparagus, and season with tarragon. Pour soup over chicken.
Cover the skillet, and bake for 15 minutes in the preheated oven. Remove cover, sprinkle with almonds, and bake for another 5 minutes.
Meanwhile, combine water and rice in a saucepan. Bring to a boil. Reduce heat, cover, and simmer for 20 minutes. Serve chicken and asparagus over rice.