- 1 large rhubarb stalk, cut into 1/2″ pieces
- 1/4 cup fresh orange juice
- 2 tablespoons honey
- 1 tablespoon finely grated peeled ginger
- 1/2 cup (1 stick) unsalted butter, room temperature
- Kosher salt, freshly ground pepper
- 1 (3 1/2–4-pounds) chicken, backbone removed, chicken patted dry
- 2 tablespoons olive oil, divided
- 1 tablespoon fresh thyme leaves
- 1 bunch asparagus, trimmed
- 2 lemons, halved
- Bring rhubarb, orange juice, honey, and ginger to a simmer in a small saucepan over medium-low heat. Cook, stirring occasionally, until rhubarb is soft but not falling apart, about 5 minutes. Drain over a small bowl. Reserve cooking liquid and rhubarb separately; let cool.
- Mix rhubarb and butter in a small bowl until smooth; season with salt and pepper. Set aside 1 tablespoon rhubarb butter for vegetables.
- Preheat oven to 400°F. Place chicken, skin side up, on a rimmed baking sheet. Gently slide your fingers underneath skin to loosen and rub flesh all over with remaining rhubarb butter (try not to tear skin). Drizzle chicken with 1 tablespoon oil and some of the reserved rhubarb cooking liquid, scatter thyme over, and season with salt and pepper.
- Roast chicken until skin is browned and crisp and meat is cooked through (juices will run clear and an instant-read thermometer inserted into the thickest part of a thigh should register 165°F), 40–50 minutes. Let rest 10 minutes.
- Meanwhile, prepare grill for mediumhigh heat (or heat a grill pan over medium-high). Toss asparagus in a large bowl with remaining 1 tablespoon oil; season with salt and pepper. Grill asparagus and lemons (cut side down), turning asparagus often, until stalks are just tender, 2–3 minutes. Let lemon halves cool.
- Toss asparagus with reserved rhubarb butter. Serve chicken and asparagus with any pan juices drizzled over with grilled lemons for squeezing over.