It is a burger that contains a burrito in between two sesame-seed buns.
Role in episode
SpongeBob makes this patty during his time as a fry cook at Taco Sombrero. Señor Taco likes it, but after his taste tester chomps the Burrito Patty, spraying its filling in the face of two bystanders, he fires SpongeBob.
Later in the episode, Senñor Taco is among the restaurant owners who fight for SpongeBob because his customers apparently liked the Burrito Patties.