Preheat your oven to 425°F and line a baking sheet with parchment paper.
Slice the sweet potato into thin, uniform matchsticks for even cooking.
In a bowl, toss the sweet potato strips with olive oil and half of the sea salt, black pepper, and garlic powder.
Spread the fries in a single layer on the baking sheet and roast for 20-25 minutes, flipping halfway through until golden.
While fries roast, gently form the ground bison into a thick patty, being careful not to overwork the meat.
Season both sides of the bison patty with the remaining sea salt, black pepper, and garlic powder.
Heat a cast-iron skillet over medium-high heat and sear the patty for 4-5 minutes per side for a perfect medium-rare.
Place the cooked bison patty inside the butter lettuce leaves and top with the red onion, tomato, and Dijon mustard.