Chop and sautee the onion in butter until soft. Cool slightly.
Carefully mix onion and all other ingredients into the ground turkey until just blended, being careful not to overwork the meat.
Form into patties. Brush a non-stick pan with olive oil. Heat pan over medium until hot. Place patties on hot pan and fry over med-hot heat 4-6 minutes without moving the burgers. Bottoms should have a dark, golden crust.
Flip and cook another 4-6 minutes. (cook times can vary depending on size and thickness of burger)
Continue frying until thermometer reads 165 and remove immediately from heat.
Serve with sesame buns, lettuce, cheese, spicy ketchup (such as Maya Kaimal brand) and sauteed curry onions-(recipe following)
Make onions by halving a sweet onion and slice in thick half-moon pieces. Melt 1-2 T butter in nonstick skillet over medium heat. Add onions and sautee 1-2 minutes. Reduce heat, sprinkle with 1/4- 1/2 teaspoon curry powder and sautee slow until onions are soft and slightly caramelized. Can make these ahead and reheat just before topping your burgers.