If you are going to cook the beets yourself, cut the beets into 3 pieces, and place them into a large pot. Make sure each slice is touching the bottom of the pot. Add water to the pot until all the beets are covered. Boil the water and cook the beets for 25 minutes, or until you can stab the beets easily with a knife.
While the beets are cooking, cook the quinoa. Add 1 cup of quinoa to a pot, along with 2 cups of water and then simmer the quinoa until it is cooked through and the water has evaporated (15-20 minutes).
Add the tuna to a large bowl, and mix it while cutting it up into smaller pieces with a fork. Add 4 Tablespoons of mayo, and 2 Tablespoons of mustard and mix it into the tuna.
Drain and wash the canned corn and beans, and add them to the bowl.
Add the cooked quinoa to the bowl.
Dice the cooked/boiled beets and add them to the bowl.
Mix well everything in the bowl together.
Then make your dressing. Mix 4 Tablespoons of olive oil, 3 Tablespoons of apple cider vinegar, 1/2 tsp of garlic powder, 1 tsp dried basil, and 1 tsp dried parsley to the bowl and mix well. Pour it into the bowl on top of the quinoa beet salad.
Add salt and pepper to taste to the salad and mix everything together one last time.