Divide the ground Argentine beef into two equal portions (about 8 oz / 225 g each). Lightly form each into a patty about 3/4 to 1 inch thick, making a shallow dimple in the center with your thumb to prevent puffing during cooking. Do not overwork the meat.

Season both sides of each patty generously with kosher salt and freshly ground black pepper just before cooking.

Heat a heavy skillet or cast-iron pan over medium-high heat until very hot. Add 1 tbs neutral oil and swirl to coat.

Place patties in the hot pan. Cook without moving for 3-4 minutes to develop a crust. Flip and cook 3-4 more minutes for medium doneness (adjust 2-3 minutes for rare, 5-6 for well done). If using cheese, place a slice on each patty in the last minute of cooking and cover the pan briefly to melt.

Remove patties to a plate and tent loosely with foil; let rest 3-4 minutes so juices redistribute.

Buns & Toppings

While patties rest, prepare toppings: slice the tomato into 1/4-inch rounds and pat lettuce leaves dry.

Spread softened butter on the cut sides of the buns. Return the skillet to medium heat (wipe if needed) and toast the buttered bun halves cut-side down 1-2 minutes until golden and slightly crisp.

Spread ketchup on the bottom bun and mayonnaise on the top bun (or to taste).

Assemble the burger: place the bottom bun with ketchup, add a lettuce leaf, then a tomato slice, set the rested beef patty (with melted cheese if used) on top, add pickles if desired, and finish with the mayo-spread top bun.