Pound chicken to 1/4 inch thickness; Cut each half into three pieces. Season with salt and pepper, and lemon pepper. In a large skillet, saute a third of the chicken at a time in butter until browned and no longer pink, about 10 minutes. Remove and keep warm. In the same skillet, saute onions until tender. Add cream, lemon juice and tarragon; bring to a boil. Cook and stir until thickened, about 5-6 minutes. Put chicken in skillet for a minute.Serve chicken over rice.