Preheat your oven to 400°F (200°C).
Wash the beets and trim off the ends. Coat them lightly with 1 tablespoon of olive oil.
Wrap each beet in foil and place on a baking tray.
Roast in the oven for about 30 minutes or until tender.
While the beets are roasting, rinse the quinoa under cold water until the water runs clear.
In a saucepan, bring 2 cups of water to a boil. Add quinoa and a pinch of salt.
Reduce the heat to medium-low and cover. Let the quinoa simmer for about 15 minutes or until the water is absorbed.
Remove from heat and let the quinoa sit for 5 minutes, then fluff with a fork.
Once the beets are cool enough to handle, peel and dice them.
In a large mixing bowl, combine the roasted beets, cooked quinoa, lemon juice, remaining olive oil, dill, salt, and pepper. Toss to mix well.
Gently fold in the feta cheese, arugula, walnuts, and red onion slices.
Adjust seasoning if necessary.