In a large skillet, heat 2 tablespoons of the reserved sundried tomato oil over medium heat.
Add the sliced onions and sauté them for a few minutes, until soft.
Reduce heat to medium-low and stir in the balsamic vinegar. Cook, stirring occasionally, until the onions are golden brown (for 30 minutes or more). Reserve.
For the Bison Burger:
Mix the ground bison meat with the sun dried tomatoes, diced onions, garlic, chipotle sauce and spices. Shape into 4 patties.
Oil the grill grates and preheat to medium. Alternatively, you can use a lightly oiled skillet over medium heat.
Grill the burgers for 4 to 5 minutes per side, or until they reach an internal temperature of 160°F for well-done. If you want the cheese melted, place the Havarti slices on top of the patties about 2 minutes before the burgers are done, with the grill lid closed.
Place the buns cut-side-down on the grill until toasted (1 to 2 minutes).
Serve the burger patties on the toasted buns with the caramelized onions (if using) and other toppings.
Notes
The nutrition information does not include the caramelized onions or toppings.
If you are pressed for time, you can skip the caramelized onions.