Step 1

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.

Step 2

Mix rhubarb and butter in a small bowl until smooth; season with salt and pepper. Set aside 1 Tbsp. rhubarb butter for vegetables.

Step 3

Preheat oven to 400°. 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 Tbsp. oil and some of the reserved rhubarb cooking liquid, scatter thyme over, and season with salt and pepper.

Step 4

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°), 40−50 minutes. Let rest 10 minutes.

Step 5

Meanwhile, prepare grill for medium-high heat (or heat a grill pan over medium-high). Toss asparagus in a large bowl with remaining 1 Tbsp. 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.

Step 6

Toss asparagus with reserved rhubarb butter. Serve chicken and asparagus with any pan juices drizzled over with grilled lemons for squeezing over.