Step 1: In a small bowl, prepare the secret sauce by whisking together mayonnaise, ketchup, yellow mustard, dill pickle relish, sugar, onion powder, and garlic powder until smooth. Set aside.
Step 2: Divide the ground beef into 8 equal 2-ounce (56g) balls. Do not overwork the meat; gently form the balls.
Step 3: Heat a large cast-iron griddle or heavy-bottomed skillet over medium-high heat until it is very hot and just starting to smoke. If needed, add a very light drizzle of oil.
Step 4: Place one tortilla onto the hot griddle. Immediately place one beef ball directly on top of the tortilla.
Step 5: Using a sturdy metal spatula and a second spatula or a heavy pot to press down, firmly smash the beef ball onto the tortilla until it is very thin, about 1/8 to 1/16 inch thick. Press firmly for 10-15 seconds to create maximum surface contact and caramelization.
Step 6: Season the raw side of the patty generously with salt and pepper.
Step 7: Cook for about 2-3 minutes, undisturbed, until the edges of the patty are crispy and browned, and you see juices bubbling through the top.
Step 8: Carefully scrape the spatula underneath the patty, ensuring you get all the crispy bits and the patty is still attached to the tortilla. Flip the patty-tortilla combo.
Step 9: Immediately place a slice of American cheese on top of the cooked patty. Cook for another 1-2 minutes, or until the cheese is melted and bubbly, and the tortilla is lightly toasted and pliable.
Step 10: Remove the Smash Burger Taco from the griddle and transfer it to a plate. Repeat with the remaining beef balls and tortillas.
Step 11: To assemble, spread a generous spoonful of the secret sauce on each cheese-covered patty-tortilla.
Step 12: Top with shredded iceberg lettuce, diced white onion, and sliced dill pickles.
Step 13: Fold the Smash Burger Taco in half and serve immediately. Enjoy your homemade Smash Burger Tacos!