Roast the vegetables: Heat the oven to 425°F and set a rack in the middle. Line a large sheet pan with parchment paper for easier cleanup.

Put the cauliflower florets and red onion wedges on the sheet pan.

Drizzle 2 tablespoons of the olive oil over the vegetables. Sprinkle with the cumin, 1/2 teaspoon of the salt, and 1/4 teaspoon of the black pepper, then toss well and spread everything into a single layer.

Slide the sheet pan into the oven and roast for 15 minutes.

Take the sheet pan out of the oven and turn the vegetables with a spatula. Return the pan to the oven and roast for 10 to 12 minutes more, until the cauliflower is tender and browned on the edges and the onion is soft. Set the pan aside.

Cook the millet: While the vegetables roast, rinse the millet in a fine-mesh sieve under cool running water for about 30 seconds. Shake off the extra water.

Set a medium saucepan over medium heat. Add 1 tablespoon of the olive oil and the millet, then stir for 1 to 2 minutes until the grains smell lightly toasted.

Pour the vegetable broth into the saucepan and add 1/2 teaspoon of the salt. Raise the heat to medium-high and bring the liquid to a boil.

Cover the saucepan, lower the heat to low, and cook for 18 to 20 minutes, until the broth is absorbed and the millet is tender. Remove the saucepan from the heat and let it stand, still covered, for 5 minutes.

Make the topping: In a small bowl, stir together the feta, chopped olives, parsley, lemon zest, and 1 tablespoon of the lemon juice. Press the mixture lightly with a fork so some of the feta softens and coats the olives.

Warm the beans: Set a medium skillet over medium heat. Add the remaining 1 tablespoon olive oil and the garlic, and cook for about 30 seconds, stirring, until the garlic smells fragrant.

Add the cannellini beans to the skillet with 2 tablespoons of water, the remaining 1/2 teaspoon salt, and the remaining 1/4 teaspoon black pepper. Cook for 3 to 4 minutes, stirring gently, until the beans are hot and glossy.