Preheat oven to 400 degrees and prepare a baking sheet with aluminum foil and non-stick spray. Throughly rinse produce and pat dry. Peel, halve, and slice onions thinly. Trim the ends off zucchini, quarter lengthwise and remove the seedy core. Cut into 3-4" sticks. Divide ground beef into four equal parts, and form each part into ½-thick patties. Season with a pinch of salt and pepper and reserve.

Heat a medium pan over medium-low heat. Add 1 tsp. of olive oil and add the onions. The onions should just barely sizzle when they hit the pan, not pop and hiss violently like a wild jungle cat. Continue cooking, stirring occasionally for 15-20 minutes, until the onions are uniformly caramelized. Reserve.

In a small bowl, whisk together the ketchup, pickle relish, and all but 2 Tbsp. of the mayonnaise. Season with a pinch of salt and pepper.

In a mixing bowl, add the buttermilk and a pinch of salt and pepper. In a separate mixing bowl, add panko breadcrumbs and Parmesan and season with a pinch of salt and pepper. Working in batches, dredge the zucchini fries in the buttermilk and then the panko. Arrange the breaded zucchini on the prepared baking sheet and bake in the oven for 12-15 minutes, or until browned and crispy. Set aside on a paper towel-lined plate.

Place two medium pans over medium on the stove. Once the pans are hot, in the first one, cook the burger patties 3-4 minutes per side, or until internal temperature reaches 145 degrees. While the patties are cooking, smear one side of each piece of bread with the reserved mayonnaise. (This is out secret to getting a perfect crust.) Place mayo side down in the pan and top each slice with the caramelized onions and Swiss cheese. Top each piece with a patty and smear the patties with the Thousand Island. Remove from pan to a plate and unite the halves into one glorious sandwich.

Allow the patty melt to cool slightly and slice in half. Serve on a plate with zucchini fries and any remaining Thousand Island for dipping.