How to Make It
Preheat the oven to 350°. Oil a parchment paperlined baking sheet. Arrange the onion slices on the parchment paper in a single layer and sprinkle all over with the Cajun spice mix. Bake the onion slices for about 30 minutes, until they are slightly dry and browned in spots.
Meanwhile, in a medium skillet, cook the bacon slices over moderate heat until crisp, about 6 minutes. Drain on paper towels and cut into 2-inch pieces.
Season the ground beef with salt and pepper and form it into 12 small hamburger patties. Arrange the dinner rolls on a large baking sheet. Place a pickle slice on the bottom half of each roll, then top with a tomato slice.
Preheat a grill pan or griddle. Brush the patties with oil and cook over high heat, turning once, until browned, about 3 minutes. Set the burgers on the dinner rolls. Top with the cheese, a few onion rings and the bacon. Cover with the buns and bake for 5 minutes for medium-rare meat. Serve right away.