Add the turkey burger ingredients to a large bowl. Using your hands, mix together well then form into 6 small burger patties, setting them aside on a plate, ready to cook.
Add a little olive oil to a small non-stick pan over medium-high heat. Add the onions and sauté for around 5 minutes, until nicely browned, stirring occasionally to ensure they don't burn. You may need to add a little water (1-2 Tbsp) about 3 minutes in, to add moisture and prevent burning.
Add the grated beets to the pan, along with balsamic vinegar, stir and allow to heat for around 30 seconds.
Add 1/4 cup water and the stevia, turn down the heat to low and simmer for around 10 minutes, stirring occasionally, until the beets and onion are nicely caramelized into a relish-texture -soft and sweet!
Meanwhile, in another large non-stick pan, heat a little olive oil over medium-high heat. Add the turkey patties and cook on each side for 4 minutes, or until cooked through.
Serve the lettuce on 2 plates, top with 2 patties for each plate, mayonnaise on top of the patties, slices of tomato on top and finally a generous pile of the beet relish.
This dish actually serves 3, so serve when you have guests over or use the remainder for another lunch or dinner.