Prepare vegetables as directed above. Add the duck fat to a large skillet and heat on medium until melted. Add the slices of turkey bacon to the pan and cook on medium heat, turning occasionally until crispy and well browned on both sides. Remove from bacon from pan and place on paper towels to drain off the excess fat. Using a pastry brush, pick up any remaining duck fat from the skillet and brush onto a griddle. Preheat the griddle to toast the bread. Spread the plant butter on one side of each slice of bread and place on the heated griddle. Brown the buttered side as desired. Flip bread and warm the other side for a minute or two.
Assemble the sandwiches. Spread mayonnaise onto the bread, layer on the lettuce, bacon, and tomato. Season the tomato slice with salt and pepper, top with the remaining slice of bread.