First, preheat your skillet over medium-high heat. While it's warming up, grate half of a medium onion on the smallest holes of a box grater — this gives you fine onion bits without too much liquid.
Measure out two tablespoons of the grated onion (drain off any extra moisture) and add it to a bowl with the ground turkey, Worcestershire sauce, kosher salt, and black pepper. Gently mix everything — don’t overwork the meat, or your burgers may become tough.
Divide the mixture into four equal balls. Add a little oil to your hot skillet, then place each ball in the pan. Immediately flatten (smash) each ball with the back of your spatula, pressing down firmly to create a thin patty.
Cook each side for about 4 minutes, or until the edges brown and crisp. If using cheese, add it during the last 2 minutes so it melts nicely.
Once cooked, remove the patties and use a meat thermometer to ensure they’ve reached 165°F internally — that’s key for turkey.
Toast your buns in the same skillet or another pan, then build your burgers with your favorite toppings and condiments. Serve immediately for the best texture.