Meals with Grilled Onion

🎃 Follow & Save for later 🎃 Smash Burger 🍔 ▪︎ 2 brioche buns1/2 lb (225 g) ▪︎ ground beef (80/20) ▪︎ Salt and black pepper ▪︎ 2 slices cheddar cheese ▪︎ Lettuce leaves ▪︎ 1 thick onion slice (grilled) ▪︎ 1 tablespoon mayonnaise1 teaspoon ketchup ▪︎ 1 teaspoon mustard ▪︎ Sweet pota