Heat the oven to 425°F and place a rack in the upper third. Set out a large sheet pan.

Put the broccoli florets, red onion wedges, and drained butter beans on the sheet pan.

Drizzle 2 tablespoons of the olive oil over the vegetables and beans.

Sprinkle the cumin, 3/4 teaspoon of the salt, and 1/4 teaspoon of the black pepper over the sheet pan. Toss well, then spread everything into a mostly even layer.

Roast for 15 minutes.

Take the sheet pan out of the oven and stir the vegetables and beans. Spread them back out and return the pan to the oven.

Roast 8 to 10 minutes more, until the broccoli has dark edges and the beans look a little wrinkled.

While the sheet pan roasts, fill a medium saucepan with water and bring it to a boil over high heat.

Add the remaining 1/2 teaspoon salt to the boiling water.

Add the pearl couscous to the saucepan.

Cook the couscous for 8 to 10 minutes, stirring once or twice, until it is tender. It should be soft but still hold its shape.

While the couscous cooks, put the lemon zest, 2 tablespoons of lemon juice, the remaining 1 tablespoon olive oil, and the remaining 1/4 teaspoon black pepper in a large bowl.