In a large skillet, melt 1 TBSP butter and toast the pretzel buns. Set aside.
In the same pan, melt another TBSP butter plus 1 TBSP Olive Oil. Cut the onion into 4 ½” slices. Cook the onion for 5 minutes per side, or until softened and caramelized. Set aside.
Season the burger patties with seasoning salt. Melt 2 TBSP butter in the same skillet and fry the burgers to your desired done-ness.
When the burgers are almost done, lay slices of Dill Havarti on top and let cheese melt.
Spread 1 TBSP mayo on the bottom buns. Add a layer of butter lettuce. Top with burgers, pickles, onion, and top buns.
Serve with waffle fries and ketchup.