Preheat the oven to 450F with one rack in the upper third of the oven and one rack in the lower third. Line a baking pan with non-stick aluminum foil. Rinse and cut the rhubarb in 3/4" lengths and place in the pan. Drizzle the honey over the rhubarb and toss to coat. Bake on the top rack of the oven for about 5 minutes or until softened. Let cool.
Meanwhile, toast the walnuts on the lower baking rack until lightly browned and fragrant, also about 5 minutes. Let cool.