Smashburgers With Sambal Special Sauce

Make the sauce:

1. Combine the mayo, mustard, and sambal in a bowl and chill until ready to use.

Make the burgers:

1. Gently combine the beef, salt, and pepper in a bowl, trying not to overwork. Form the meat into four equal-sized, 5-ounce balls. Heat a very large skillet—my Family Pan is perfect—over high heat until very, very hot but not smoking. (Make sure you start with a clean pan with no stuck-on bits that can burn!)

2. Add the oil, then brush it all over the skillet with a heatproof (read: silicone) pastry brush; the oil should basically shimmer upon contact. Add the burgers to the skillet, leaving even space between the burgers, and smash down using a large, flat spatula, alternating between burgers as they cook and flatten to about ½ inch high by 5 inches wide.

3. Meanwhile, arrange the onion rings around the burgers and let them start to cook, moving occasionally in the beef fat and juices as they emerge from the burgers.

4. After the burgers are crispy, with a hard, dark shell underneath (about 2–2 ½ minutes), flip the burgers and continue to cook, pressing down, until medium-rare, another 1–1 ½ minutes.

5. Remove the burgers to a plate and stir the onions around another 30 seconds until charred and softened. Spread a generous tablespoon of the special sauce on each side of each bun, then layer two lettuce leaves, topped by a burger patty, some charred onions, and tomato slices. Close the burgers and serve ASAP!