California Beet Burger

Name: California Beet Burger
Ingredients: 2 cups thinly sliced red onion; 1/2 cup apple cider vinegar; 1/2 cup filtered water; 1 tablespoon agave nectar; 1 1/2 teaspoons sea salt; 1/8 teaspoon dried dill; 1/8 teaspoon ground black pepper; 2 tablespoons extra-virgin olive oil, plus more for the pans; 1 cup shredded beets; 1 cup cooked brown rice; 1 cup sunflower seeds; 1/2 cup diced onion; 2 tablespoons nutritional yeast; 1 tablespoon gluten-free vegan tamari; 1 1/2 teaspoons Italian seasoning; 3/4 teaspoon sea salt; 1/4 teaspoon ground black pepper; 1 small clove garlic; 1 cup raw cashews; 3/4 cup plus 2 tablespoons filtered water; 1/2 cup nutritional yeast; 2 tablespoons extra-virgin olive oil; 1 tablespoon apple cider vinegar; Extra-virgin olive oil, for the pans; Plant-based vegan butter of choice; 8 slices favorite vegan bread; 1 avocado, mashed; 4 large slices tomato; 1 cup alfalfa sprouts