Beat eggs in 2 separate small bowls. Place flour and crushed cornflakes into 2 shallow bowls.

Mix 1 beaten egg, ground beef, onion, salt, and pepper in a bowl. Form into 3 equal-sized patties.

Dip each beef patty into flour, followed by beaten egg. Coat completely with crushed cornflakes.

Heat oil in a large skillet over medium-high heat. Cook burgers for 5 minutes, flip, and continue cooking to your desired degree of doneness, about 4 minutes. An instant-read thermometer inserted into the center should read at least 160 degrees F (70 degrees C).